Polycarbonate resins and processes for producing the same

ABSTRACT

The invention is to provide polycarbonate resins having excellent light resistance, transparency, hue, heat resistance, thermal stability, and mechanical strength and to provide processes for efficiently and stably producing a polycarbonate resin which stably shows those performances. The invention includes: polycarbonate resins which at least contain structural units derived from a dihydroxy compound having the portion represented by the following general formula (1) as part of the structure thereof and which have specific properties; and processes for producing the polycarbonate resins. 
       [Chem. 1] 
       CH 2 —O  (1)
 
     (The case where the portion represented by general formula (1) is part of —CH 2 —O—H is excluded.)

TECHNICAL FIELD

The present invention relates to polycarbonate resins having excellentlight resistance, transparency, hue, heat resistance, thermal stability,and mechanical strength and to processes for efficiently and stablyproducing the polycarbonate resins which stably show these performances.

BACKGROUND ART

Polycarbonate resins are generally produced using bisphenols as amonomer ingredient, and are being extensively utilized as so-calledengineering plastics in the fields of electrical/electronic parts,automotive parts, medical parts, building materials, films, sheets,bottles, optical recording media, lenses, etc. so as to take advantageof the superiority thereof such as transparency, heat resistance, andmechanical strength.

However, the conventional polycarbonate resins deteriorate in hue,transparency, and mechanical strength when used over a long period inplaces where the resins are exposed to ultraviolet rays or visiblelight. There hence have been limitations on outdoor use thereof and onuse thereof in the vicinity of illuminators.

Techniques in which a benzophenone-based ultraviolet absorber,benzotriazole-based ultraviolet absorber, or benzoxazine-basedultraviolet absorber is added to a polycarbonate resin in order toovercome such problems are widely known (see, for example, non-patentdocument 1).

However, addition of such an ultraviolet absorber poses the followingproblems although the addition brings about improvements in hueretention through ultraviolet irradiation, etc. Namely, there have beenproblems, for example, that the addition of the ultraviolet absorberdeteriorates the hue, heat resistance, and transparency which areinherent in the resin and that the ultraviolet absorber volatilizesduring molding to foul the mold.

The bisphenol compounds for use in producing conventional polycarbonateresins have a benzene ring structure and hence show high absorption ofultraviolet rays.

This leads to a deterioration in the light resistance of thepolycarbonate resins. Consequently, use of monomer units derived from analiphatic dihydroxy compound or alicyclic dihydroxy compound which hasno benzene ring structure in the molecular framework or from a cyclicdihydroxy compound having an ether bond in the molecule, such asisosorbide, is expected to theoretically improve light resistance. Inparticular, polycarbonate resins produced using, as a monomer,isosorbide obtained from biomass resources have excellent heatresistance and mechanical strength, and many investigations thereonhence have come to be made in recent years (see, for example, patentdocuments 1 to 6).

However, since the aliphatic dihydroxy compound or alicyclic dihydroxycompound and the cyclic dihydroxy compound having an ether bond in themolecule, such as isosorbide, have no phenolic hydroxyl group, it isdifficult to polymerize these compounds by the interfacial process whichis widely known as a process for polycarbonate resin production usingbisphenol A as a starting material. Usually, polycarbonate resins areproduced from those compounds by the process which is called atransesterification process or a melt process. In this process, thedihydroxy compound and a carbonic diester, e.g., diphenyl carbonate, aresubjected to transesterification at a high temperature of 200° C. orabove in the presence of a basic catalyst, and the by-product, e.g.,phenol, is removed from the system to allow the polymerization toproceed, thereby obtaining a polycarbonate resin. However, thepolycarbonate resins obtained using monomers having no phenolic hydroxylgroup, such as those shown above, have poor thermal stability ascompared with polycarbonate resins obtained using monomers havingphenolic hydroxyl groups, e.g., bisphenol A, and hence have had thefollowing problem. The polycarbonate resins take a color during thepolymerization or molding in which the resins are exposed to hightemperatures and, as a result, the polycarbonate resins come to absorbultraviolet rays and visible light and hence have impaired lightresistance. Especially when a monomer having an ether bond in themolecule, such as isosorbide, was used, the polycarbonate resinconsiderably deteriorates in hue. A significant improvement has beendesired.

Meanwhile, as stated above, polycarbonate resins are extensivelyutilized as so-called engineering plastics in the fields ofelectrical/electronic parts and automotive parts and in optical fieldssuch as optical recording media, lenses, etc. However, for use asoptical compensation films for flat panel displays, which are rapidlyspreading recently, the films have come to be required to have higheroptical properties including low birefringence and a low photoelasticcoefficient. The existing aromatic polycarbonates have come to be unableto meet the requirement.

Conventional polycarbonates are produced from starting materials derivedfrom petroleum resources. In recent years, however, there is a fearabout depletion of petroleum resources, and there is a need for apolycarbonate produced using a starting material obtained from biomassresources including plants. In addition, there is a fear that the globalwarming caused by increases in carbon dioxide emission and by carbondioxide accumulation may bring about climate changes and the like. Alsofrom this standpoint, there is a desire for development of apolycarbonate which is produced from a plant-derived monomer and whichis carbon-neutral even when discarded after use.

Under these circumstances, a process has been proposed in which aspecial dihydroxy compound is subjected as a monomer ingredient totransesterification with a carbonic diester to obtain a polycarbonatewhile removing the by-product monohydroxy compound by distillation undervacuum, as described in patent documents 1 to 6.

However, such a dihydroxy compound having a special structure has alower boiling point than bisphenols and hence volatilizes considerablyduring the transesterification reaction, which is conducted at a hightemperature and a reduced pressure. The volatilization thereof resultsnot only in a decrease in material unit but also in a problem that it isdifficult to regulate the concentration of end groups, which affectsquality, to a given value. Furthermore, there has been a problem thatwhen a plurality of dihydroxy compounds are used, the molar proportionsof the dihydroxy compounds used change during the polymerization, makingit impossible to obtain a polycarbonate resin having a desired molecularweight and a desired composition.

Expedients which may be usable for overcoming those problems include tolower the polymerization temperature and to lessen the degree of vacuum.However, use of these expedients poses a dilemma that monomervolatilization is inhibited but a decrease in productivity results.

A technique in which a polymerization reactor having a specific refluxcondenser is used has also been proposed (see, for example, patentdocument 7). However, the improvement in material unit is still on anunsatisfactory level, and a further improvement is desired.

In addition, the by-product monohydroxy compound, when removed bydistillation, deprives the system of a large amount of latent heat ofvaporization. Consequently, for maintaining a given polymerizationtemperature, it is necessary to heat the system with a heating medium(heat medium). In a larger-scale apparatus, however, the heat-transfersurface within the reactor has a reduced area per unit amount of theliquid reaction mixture and, hence, it becomes necessary to heat thereactor with a heat medium having a higher temperature. This means thatthe part of the liquid reaction mixture which is in contact with thesurface of the wall through which the heat medium flows is heated at ahigher temperature. Namely, not only volatilization of the low-boilingdihydroxy compound which is in contact with the wall surface isconsiderably accelerated, but also there is a problem that the heatingcauses thermal deterioration in the vicinity of the wall surface,resulting in a quality deterioration. This problem becomes more seriousas the scale increases.

PRIOR-ART DOCUMENTS Patent Documents

-   Patent Document 1: International Publication No. 04/111106-   Patent Document 2: JP-A-2006-232897-   Patent Document 3: JP-A-2006-28441-   Patent Document 4: JP-A-2008-24919-   Patent Document 5: JP-A-2009-91404-   Patent Document 6: JP-A-2009-91417-   Patent Document 7: JP-A-2008-56844

Non-Patent Document

-   Non-Patent Document 1: HONMA Seiichi, ed., Porikabonēto Jushi    Handobukku, The Nikkan Kogyo Shinbun, Ltd., Aug. 28, 1992.

SUMMARY OF THE INVENTION Problems that the Invention is to Solve

An object of the invention is to eliminate the problems of prior-arttechniques described above and to provide a polycarbonate resin havingexcellent light resistance, transparency, hue, heat resistance, thermalstability, and mechanical strength.

Another object of the invention is to eliminate the problems ofprior-art techniques and to provide a process for efficiently and stablyproducing a polycarbonate resin which has excellent light resistance,transparency, hue, heat resistance, thermal stability, and mechanicalstrength and has performance stability.

Means for Solving the Problems

The present inventors diligently made investigations in order toovercome those problems. As a result, the inventors have found that apolycarbonate resin which has the structure represented by the followinggeneral formula (1) in the molecule and which has a transmittance, asmeasured at a specific wavelength, of a specific value or higher notonly has excellent light resistance but also has excellent transparency,hue, heat resistance, thermal stability, and mechanical strength. Afirst aspect of the invention has been thus achieved.

The first aspect of the invention resides in the following [1] to [16].

[1] A polycarbonate resin which at least contains structural unitsderived from a dihydroxy compound having the portion represented by thefollowing general formula (1) as part of the structure thereof, thepolycarbonate resin giving a molded object (thickness, 3 mm) which has alight transmittance, as measured at a wavelength of 350 nm, of 60% orhigher.

[Chem. 1]

CH₂—O  (1)

(The case where the portion represented by general formula (1) is partof —CH₂—O—H is excluded.)[2] The polycarbonate resin according to [1] above wherein the moldedobject (thickness, 3 mm) formed from the polycarbonate resin has a lighttransmittance, as measured at a wavelength of 320 nm, of 30% or higher.[3] The polycarbonate resin according to [1] or [2] above wherein themolded object (thickness, 3 mm) formed from the polycarbonate resin hasa yellowness index (YI) value, as measured with respect to transmittedlight in accordance with ASTM D1925-70, of 12 or less after having beenirradiated with light for 100 hours using a metal halide lamp in anenvironment of 63° C. and a relative humidity of 50% at an irradiancefor the wavelength range of 300-400 nm of 1.5 kW/m².[4] The polycarbonate resin according to any one of [1] to [3] abovewherein the molded object (thickness, 3 mm) formed from thepolycarbonate resin has an initial yellowness index value of 10 or less.[5] The polycarbonate resin according to any one of [1] to [4] abovewherein the difference between the initial yellowness index value of themolded object (thickness, 3 mm) formed from the polycarbonate resin andthe yellowness index (YI) value thereof measured with respect totransmitted light in accordance with ASTM D1925-70 after the moldedobject has been irradiated with light for 100 hours using a metal halidelamp in an environment of 63° C. and a relative humidity of 50% at anirradiance for the wavelength range of 300-400 nm of 1.5 kW/m² is 6 orless in terms of absolute value.[6] The polycarbonate resin according to any one of [1] to [5] abovewherein the molded object (thickness, 3 mm) formed from thepolycarbonate resin has an L* value of 96.3 or higher.[7] The polycarbonate resin according to any one of [1] to [6] abovewhich contains a carbonic diester represented by the following generalformula (2) in an amount of 60 weight ppm or less.

(In general formula (2), A¹ and A² each independently are a substitutedor unsubstituted aliphatic group having 1-18 carbon atoms or asubstituted or unsubstituted aromatic group.)[8] The polycarbonate resin according to any one of [1] to [7] abovewhich contains an aromatic monohydroxy compound in an amount of 700weight ppm or less.[9] The polycarbonate resin according to any one of [1] to [8] abovewhich has a total content of sodium, potassium, and cesium of 1 weightppm or less in terms of metal amount.[10] The polycarbonate resin according to any one of [1] to [9] abovewherein the concentration of the end group represented by the followinggeneral formula (3) in the polycarbonate resin is 20-160 μeq/g.

[11] The polycarbonate resin according to any one of [1] to [10] abovewhich satisfies A/(A+B)≦0.1, wherein A is the number of moles of the Hbonded to the aromatic rings contained in the polycarbonate resin and Bis the number of moles of the H bonded to the part other than thearomatic rings.[12] The polycarbonate resin according to any one of [1] to [11] abovewherein the dihydroxy compound having the portion represented by generalformula (1) as part of the structure thereof is a dihydroxy compoundrepresented by the following general formula (4).

[13] The polycarbonate resin according to any one of [1] to [12] abovewhich further contains structural units derived from at least onecompound selected from the group consisting of aliphatic dihydroxycompounds and alicyclic dihydroxy compounds.[14] The polycarbonate resin according to any one of [1] to [13] abovewhich is obtained by condensation-polymerizing a dihydroxy compoundhaving the portion represented by general formula (1) as part of thestructure thereof with a carbonic diester represented by the followinggeneral formula (2) in the presence of a catalyst.

(In general formula (2), A¹ and A² each independently are a substitutedor unsubstituted aliphatic group having 1-18 carbon atoms or asubstituted or unsubstituted aromatic group.)[15] The polycarbonate resin according to [14] above wherein thecatalyst comprises one or more compounds of at least one metal selectedfrom the group consisting of lithium and the Group-2 metals of thelong-form periodic table, and the total amount of these compounds is 20μmol or less in terms of metal amount per mole of the dihydroxy compoundused.[16] The polycarbonate resin according to any one of [1] to [14] abovewhich has been obtained using as a catalyst at least one metal compoundselected from the group consisting of magnesium compounds and calciumcompounds, the polycarbonate resin having a total content of lithium,sodium, potassium, and cesium of 1 weight ppm or less in terms of metalamount.

The inventors diligently made further investigations. As a result, theinventors have found that a polycarbonate resin which has the structurerepresented by the following general formula (1) in the molecule andwhich has a transmittance, as measured at a specific wavelength, of aspecific value or higher not only has excellent light resistance butalso has excellent transparency, hue, heat resistance, thermalstability, and mechanical strength. A second aspect of the invention hasbeen thus achieved.

The second aspect of the invention resides in the following [17] to[20].

[17] A polycarbonate resin which at least contains structural unitsderived from a dihydroxy compound having the portion represented by thefollowing general formula (1) as part of the structure thereof, thepolycarbonate resin giving a molded object (thickness, 3 mm) which has ayellowness index (YI) value, as measured with respect to transmittedlight in accordance with ASTM D1925-70, of 12 or less after having beenirradiated with light for 100 hours using a metal halide lamp in anenvironment of 63° C. and a relative humidity of 50% at an irradiancefor the wavelength range of 300-400 nm of 1.5 kW/m².

[Chem. 6]

CH₂—O  (1)

(The case where the portion represented by general formula (1) is partof —CH₂—O—H is excluded.)[18] The polycarbonate resin according to [17] above wherein the moldedobject (thickness, 3 mm) formed from the polycarbonate resin has aninitial yellowness index value of 10 or less.[19] The polycarbonate resin according to [17] or [18] above wherein thedifference between the initial yellowness index value of the moldedobject (thickness, 3 mm) formed from the polycarbonate resin and theyellowness index (YI) value thereof measured with respect to transmittedlight in accordance with ASTM D1925-70 after the molded object has beenirradiated with light for 100 hours using a metal halide lamp in anenvironment of 63° C. and a relative humidity of 50% at an irradiancefor the wavelength range of 300-400 nm of 1.5 kW/m² is 6 or less interms of absolute value.[20] The polycarbonate resin according to any one of [17] to [19] abovewherein the molded object (thickness, 3 mm) formed from thepolycarbonate resin has a light transmittance, as measured at awavelength of 350 nm, of 60% or higher.

The inventors diligently made still further investigations. As a result,the inventors have found that a polycarbonate resin which has beenobtained by condensation-polymerizing at least one dihydroxy compoundincluding a dihydroxy compound that has the portion represented by thefollowing general formula (1) as part of the structure thereof with acarbonic diester represented by the following general formula (2) in thepresence of a catalyst comprising one or more compounds containing atleast one metal selected from the group consisting of lithium and theGroup-2 metals of the long-form periodic table, and in which the contentof the metal-containing compounds is 20 μmol or less in terms of metalamount per mole of the dihydroxy compound and the content of an aromaticmonohydroxy compound is 700 weight ppm or less not only has excellentlight resistance but also has excellent transparency, hue, heatresistance, thermal stability, and mechanical strength. A third aspectof the invention has been thus achieved.

The third aspect of the invention resides in the following [21] to [34].

[21] A polycarbonate resin obtained by condensation-polymerizing atleast one dihydroxy compound including a dihydroxy compound which hasthe portion represented by the following general formula (1) as part ofthe structure thereof with a carbonic diester represented by thefollowing general formula (2) in the presence of a catalyst, thecatalyst comprising one or more compounds containing at least one metalselected from the group consisting of lithium and the Group-2 metals ofthe long-form periodic table, the polycarbonate resin having a contentof the metal-containing compounds of 20 μmol or less in terms of metalamount per mole of the dihydroxy compound and containing an aromaticmonohydroxy compound in an amount of 700 weight ppm or less.

[Chem. 7]

CH₂—O  (1)

(The case where the portion represented by general formula (1) is partof —CH₂—O—H is excluded.)

(In general formula (2), A¹ and A² each independently are a substitutedor unsubstituted aliphatic group having 1-18 carbon atoms or asubstituted or unsubstituted aromatic group.)[22] The polycarbonate resin according to [21] above wherein thecatalyst comprises at least one metal compound selected from the groupconsisting of magnesium compounds and calcium compounds.[23] The polycarbonate resin according to [21] or [22] above which has atotal content of sodium, potassium, and cesium of 1 weight ppm or lessin terms of metal amount.[24] The polycarbonate resin according to any one of [21] to [23] abovewhich has a total content of lithium, sodium, potassium, and cesium of 1weight ppm or less in terms of metal amount.[25] The polycarbonate resin according to any one of [21] to [24] abovewhich contains the carbonic diester represented by general formula (2)in an amount of 60 weight ppm or less.[26] The polycarbonate resin according to any one of [21] to [25] abovewherein the dihydroxy compound having the portion represented by generalformula (1) as part of the structure thereof is a compound representedby the following general formula (4).

[27] The polycarbonate resin according to any one of [21] to [26] abovewhich contains structural units derived from the dihydroxy compound thathas the portion represented by general formula (1) as part of thestructure thereof and further contains structural units derived from atleast one compound selected from the group consisting of aliphaticdihydroxy compounds and alicyclic dihydroxy compounds.[28] The polycarbonate resin according to any one of [21] to [27] abovewherein the concentration of the end group represented by the followinggeneral formula (3) in the polycarbonate resin is 20-160 μeq/g.

[29] The polycarbonate resin according to any one of [21] to [28] abovewhich satisfies A/(A+B)≦0.1, wherein A is the number of moles of the Hbonded to the aromatic rings contained in the polycarbonate resin and Bis the number of moles of the H bonded to the part other than thearomatic rings.[30] The polycarbonate resin according to any one of [21] to [29] abovewherein a molded object (thickness, 3 mm) formed from the polycarbonateresin has a light transmittance, as measured at a wavelength of 350 nm,of 60% or higher.[31] The polycarbonate resin according to any one of [21] to [30] abovewherein a molded object (thickness, 3 mm) formed from the polycarbonateresin has a light transmittance, as measured at a wavelength of 320 nm,of 30% or higher.[32] The polycarbonate resin according to any one of [21] to [31] abovewherein a molded object (thickness, 3 mm) formed from the polycarbonateresin has a yellowness index (YI) value, as measured with respect totransmitted light in accordance with ASTM D1925-70, of 12 or less afterhaving been irradiated with light for 100 hours using a metal halidelamp in an environment of 63° C. and a relative humidity of 50% at anirradiance for the wavelength range of 300-400 nm of 1.5 kW/m².[33] The polycarbonate resin according to any one of [21] to [32] abovewherein a molded object (thickness, 3 mm) formed from the polycarbonateresin has an initial yellowness index value of 10 or less.[34] The polycarbonate resin according to any one of [21] to [33] abovewherein the difference between the initial yellowness index value of amolded object (thickness, 3 mm) formed from the polycarbonate resin andthe yellowness index (YI) value thereof measured with respect totransmitted light in accordance with ASTM D1925-70 after the moldedobject has been irradiated with light for 100 hours using a metal halidelamp in an environment of 63° C. and a relative humidity of 50% at anirradiance for the wavelength range of 300-400 nm of 1.5 kW/m² is 6 orless in terms of absolute value.

From the standpoint of eliminating the problems described above, it ispreferred that the invention should provide the molded articles shownbelow under [35] and [36].

[35] A molded polycarbonate resin obtained by molding the polycarbonateresin according to any one of [1] to [34] above.[36] The molded polycarbonate resin according to [35] above which is amolded article obtained by injection molding.

The inventors diligently made still further investigations. As a result,the inventors have found out a process for producing a polycarbonateresin having excellent light resistance, transparency, hue, heatresistance, thermal stability, and mechanical strength and havingstability of these performances, the process being a process in which acarbonic diester and a dihydroxy compound are used as monomers andcondensation-polymerized by a transesterification method to produce apolycarbonate resin while regulating the amount of the monomers whichare distilled off from the reactors to an amount not larger than aspecific value. A fourth aspect of the invention has been thus achieved.

The fourth aspect of the invention resides in the following [37] to[53].

[37] A process for producing a polycarbonate resin using a carbonicdiester and at least one dihydroxy compound as starting-materialmonomers and a catalyst, by condensation-polymerizing thestarting-material monomers by means of a transesterification reactionusing a plurality of reactors in multiple stages, wherein

the dihydroxy compound comprises a dihydroxy compound having the portionrepresented by the following general formula (1) as part of thestructure thereof,

at least one of the reactors from which the monohydroxy compoundgenerated as a by-product of the transesterification reaction isdistilled off in an amount at least 20% of a theoretical distillationremoval amount is a reactor which has a capacity of 20 L or more andwhich is equipped with a heating means for heating the reactor by meansof a heating medium and further equipped with a reflux condenser, thedifference between the temperature of the heating medium and thetemperature of the liquid reaction mixture present in the reactor being5° C. or more, and

the total amount of the monomers which are distilled off in all reactionstages is up to 10% by weight of the sum of the starting-materialmonomers.

[Chem. 11]

CH₂—O  (1)

(The case where the portion represented by general formula (1) is partof —CH₂—O—H is excluded.)[38] A process for producing a polycarbonate resin using a carbonicdiester and at least one dihydroxy compound as starting-materialmonomers and a catalyst, by condensation-polymerizing thestarting-material monomers by means of a transesterification reactionusing a plurality of reactors in multiple stages, wherein

the dihydroxy compound comprises a plurality of dihydroxy compounds, atleast one of which is a dihydroxy compound having the portionrepresented by the following general formula (1) as part of thestructure thereof,

at least one of the reactors from which the monohydroxy compoundgenerated as a by-product of the transesterification reaction isdistilled off in an amount at least 20% of a theoretical distillationremoval amount is a reactor which has a capacity of 20 L or more andwhich is equipped with a heating means for heating the reactor by meansof a heating medium and further equipped with a reflux condenser, thedifference between the temperature of the heating medium and thetemperature of the liquid reaction mixture present in the reactor being5° C. or more, and

the value obtained by dividing the difference between the molarproportion in percentage of each dihydroxy compound which is being fedas a starting material to the reactors and the molar proportion inpercentage of structural units of the dihydroxy compound which arecontained in the resultant polycarbonate resin by the molar proportionin percentage of the dihydroxy compound which is being fed is 0.03 orless in terms of absolute value with respect to at least one dihydroxycompound and is not larger than 0.05 in terms of absolute value withrespect to each of all dihydroxy compounds.

[Chem. 12]

CH₂—O  (1)

(The case where the portion represented by general formula (1) is partof —CH₂—O—H is excluded.)[39] The process for producing a polycarbonate resin according to [37]or [38] above wherein the dihydroxy compound comprises at least onedihydroxy compound which has a boiling point at atmospheric pressure of300° C. or lower.[40] The process for producing a polycarbonate resin according to anyone of [37] to[39] above wherein at least three reactors are used.[41] The process for producing a polycarbonate resin according to anyone of [37] to[40] above wherein a coolant is introduced into the reflux condenser,the coolant having a temperature of 45-180° C. as measured at the inletof the reflex condenser.[42] The process for producing a polycarbonate resin according to anyone of [37] to[41] above wherein the total amount of monomers which are distilled offin all reaction stages is 3% by weight or less based on the sum of thestarting-material monomers.[43] The process for producing a polycarbonate resin according to anyone of [37] to[42] above wherein one or more compounds of at least one metal selectedfrom the group consisting of lithium and the Group-2 metals of thelong-form periodic table are supplied as the catalyst to the firstreactor from which the monohydroxy compound generated as a by-product ofthe transesterification reaction is distilled off in an amount of atleast 20% of a theoretical distillation removal amount, the metalcompounds being used in an amount of 20 μmol or less in terms of thetotal amount of the metal atoms thereof per mole of all dihydroxycompounds used as starting materials.[44] The process for producing a polycarbonate resin according to [43]above wherein the catalyst comprises at least one metal compoundselected from the group consisting of magnesium compounds and calciumcompounds.[45] The process for producing a polycarbonate resin according to anyone of [37] to[44] above wherein the liquid reaction mixture in all reaction stageshas a maximum temperature lower than 250° C.[46] The process for producing a polycarbonate resin according to anyone of [37] to[45] above wherein the heating medium has a maximum temperature lowerthan 265° C.[47] The process for producing a polycarbonate resin according to anyone of [37] to[46] above wherein the dihydroxy compound comprises a compound of thefollowing general formula (4) and at least one compound selected fromthe group consisting of aliphatic dihydroxy compounds and alicyclicdihydroxy compounds.

[48] A polycarbonate resin obtained by the process according to any oneof [37] to [47] above, the polycarbonate resin giving a molded object(thickness, 3 mm) which has a light transmittance, as measured at awavelength of 350 nm, of 60% or higher.[49] A polycarbonate resin obtained by the process according to any oneof [37] to [47] above, the polycarbonate resin giving a molded object(thickness, 3 mm) which has a light transmittance, as measured at awavelength of 320 nm, of 30% or higher.[50] A polycarbonate resin obtained by the process according to any oneof [37] to [47] above, the polycarbonate resin giving a molded object(thickness, 3 mm) which has a yellowness index (YI) value, as measuredwith respect to transmitted light in accordance with ASTM D1925-70, of12 or less after having been irradiated with light for 100 hours using ametal halide lamp in an environment of 63° C. and a relative humidity of50% at an irradiance for the wavelength range of 300-400 nm of 1.5kW/m².[51] A polycarbonate resin obtained by the process according to any oneof [37] to [47] above, the polycarbonate resin giving a molded object(thickness, 3 mm) which has an initial yellowness index value of 10 orless.[52] A polycarbonate resin obtained by the process according to any oneof [37] to [47] above wherein the difference between the initialyellowness index value of a molded object (thickness, 3 mm) formed fromthe polycarbonate resin and the yellowness index (YI) value thereofmeasured with respect to transmitted light in accordance with ASTMD1925-70 after the molded object has been irradiated with light for 100hours using a metal halide lamp in an environment of 63° C. and arelative humidity of 50% at an irradiance for the wavelength range of300-400 nm of 1.5 kW/m² is 6 or less in terms of absolute value.[53] A polycarbonate resin obtained by the process according to any oneof [37] to [47] above, the polycarbonate resin giving a molded object(thickness, 3 mm) which has an L* value of 96.3 or higher.

Effects of the Invention

According to the invention, polycarbonate resins which not only haveexcellent light resistance but also have excellent transparency, hue,heat resistance, thermal stability, moldability, and mechanical strengthcan be provided. Consequently, the invention can provide polycarbonateresins which are applicable to a wide range of fields including thefield of injection molding, such as electrical/electronic parts andautomotive parts, the field of films and sheets, the field of bottlesand containers, lens applications such as camera lenses, finder lenses,and lenses for CCDs or CMOSs, films or sheets such as retardation films,diffusing sheets, and polarizing films which are utilized inliquid-crystal or plasma displays and the like, optical disks, opticalmaterials, optical parts, and binders for fixing colorants, chargetransfer agents, etc. In particular, it is possible to providepolycarbonate resins suitable for use in applications in which theresins are exposed to light including ultraviolet rays, such as outdooror lighting parts.

Furthermore, according to the invention, it is possible to efficientlyand stably produce the polycarbonate resins.

MODES FOR CARRYING OUT THE INVENTION

Modes for carrying out the invention will be explained below in detail.The following explanations on constituent elements are for embodiments(representative embodiments) of the invention, and the invention shouldnot be construed as being limited to the embodiments unless theinvention departs from the spirit thereof.

First Polycarbonate Resin

The first polycarbonate resin of the invention is a polycarbonate resinwhich at least contains structural units derived from a dihydroxycompound having the portion represented by the following general formula(1) as part of the structure thereof, and is characterized by giving amolded object (thickness, 3 mm) which has a light transmittance, asmeasured at a wavelength of 350 nm, of 60% or higher. The lighttransmittance thereof at that wavelength is preferably 65% or higher,especially preferably 70% or higher. When the light transmittancethereof at that wavelength is less than 60%, there are the cases wherethis resin shows enhanced absorption and has impaired light resistance.

[Chem. 14]

CH₂—O  (1)

(The case where the portion represented by general formula (1) is partof —CH₂—O—H is excluded.)

This is based on the finding that even when resins show no absorption ofvisible light and appear to have no color when viewed through the humaneyes, some of the resins take a color upon exposure to sunlight,artificial lighting, or the like and others do not, and also on thefinding that this problem can unexpectedly be overcome by regulating thetransmittance of light having a specific wavelength to a given value orhigher.

It is preferred that the first polycarbonate resin of the inventionshould be one in which the molded object (flat plate having a thicknessof 3 mm) formed from the resin has a light transmittance, as measured ata wavelength of 320 nm, of 30% or higher. This light transmittance ofthe molded object is more preferably 40% or higher, especiallypreferably 50% or higher. When the light transmittance thereof at thatwavelength is lower than 30%, there are the cases where the resin hasimpaired light resistance.

It is preferred that the first polycarbonate resin of the inventionshould be one in which the molded object (flat plate having a thicknessof 3 mm) formed from the polycarbonate resin has a yellowness index (YI)value, as measured with respect to transmitted light in accordance withASTM D1925-70, of 12 or less after having been irradiated with light for100 hours using a metal halide lamp in an environment of 63° C. and arelative humidity of 50% at an irradiance for the wavelength range of300-400 nm of 1.5 kW/m². The yellowness index value thereof is morepreferably 10 or less, especially preferably 8 or less. When theyellowness index (YI) value thereof exceeds 12, there are the caseswhere the resin, even when colorless immediately after molding, takes acolor upon exposure to light including ultraviolet light.

The irradiation using a metal halide lamp in the invention is anoperation in which light mainly having wavelengths of 300-400 nm (lighthaving wavelengths outside that wavelength range has been removed asmuch as possible) is irradiated upon the sample for 100 hours at anirradiance of 1.5 kW/m² by means of a specific apparatus using aspecific filter or the like, as will be described later.

It is preferred that the first polycarbonate resin of the inventionshould be one which, when molded into a flat plate having a thickness of3 mm and examined, without being subjected to the irradiation using ametal halide lamp as described above or the like, has a yellowness indexvalue (i.e., initial yellowness index value; referred to as initial YIvalue) as measured with respect to transmitted light of generally 10 orless.

The initial YI value thereof is more preferably 7 or less, especiallypreferably 5 or less.

The difference in yellowness index value between before and after themetal halide lamp irradiation is preferably 6 or less, more preferably 4or less, especially preferably 3 or less, in terms of absolute value.

When the initial yellowness index (YI) value thereof exceeds 10, thereare the cases where this resin has impaired light resistance. In thecase where the absolute value of the difference in yellowness index (YI)value between before and after the metal halide lamp irradiation exceeds6, there is a possibility that the resin might take a color when exposedto sunlight, artificial lighting, or the like over a long period tobecome unusable in applications where transparency is especiallyrequired and in other applications.

Furthermore, it is preferred that the first polycarbonate resin of theinvention should be one which, when molded into a flat plate having athickness of 3 mm and examined, has an L* value, as provided for byInternational Illumination Commission (CIE) and measured with respect totransmitted light, of generally 96.3 or higher. The L* value thereof ismore preferably 96.6 or higher, especially preferably 96.8 or higher.When the L* value thereof is less than 96.3, there are the cases wherethe resin has impaired light resistance.

Second Polycarbonate Resin

The second polycarbonate resin of the invention is a polycarbonate resinwhich at least contains structural units derived from a dihydroxycompound having the portion represented by the following general formula(1) as part of the structure thereof, and is characterized by giving amolded object (thickness, 3 mm) which has a yellowness index (YI) value,as measured with respect to transmitted light in accordance with ASTMD1925-70, of 12 or less after having been irradiated with light for 100hours using a metal halide lamp in an environment of 63° C. and arelative humidity of 50% at an irradiance for the wavelength range of300-400 nm of 1.5 kW/m².

The yellowness index (YI) value thereof is preferably 10 or less,especially preferably 8 or less.

(The case where the portion represented by general formula (1) is partof —CH₂—O—H is excluded.)

This is based on the finding that there are the cases where resins inwhich the yellowness index (YI) value, as measured in accordance withASTM D 1925-70 after 100-hour irradiation with light using the metalhalide lamp at an irradiance for the wavelength range of 300-400 nm of1.5 kW/m², is higher than 12 take a color upon exposure to lightincluding ultraviolet light even when colorless immediately aftermolding, and also on the finding that this problem can unexpectedly beovercome by regulating the heat history which the resins underwent inthe transesterification reaction (i.e., polycondensation reaction), thecatalyst used, the metal component contained therein, the content of asubstance having a specific molecular structure, etc.

It is preferred that the second polycarbonate resin of the inventionshould be one which, when molded into a flat plate having a thickness of3 mm and examined, without being subjected to the irradiation using ametal halide lamp as described above or the like, has a yellowness indexvalue (i.e., initial yellowness index value; referred to as initial YIvalue) as measured with respect to transmitted light of generally 10 orless.

The initial YI value thereof is more preferably 7 or less, especiallypreferably 5 or less.

The difference in yellowness index value between before and after themetal halide lamp irradiation is preferably 6 or less, more preferably 4or less, especially preferably 3 or less, in terms of absolute value.

When the initial yellowness index (YI) value thereof exceeds 10, thereare the cases where this resin has impaired light resistance. In thecase where the absolute value of the difference in yellowness index (YI)value between before and after the metal halide lamp irradiation exceeds6, there is a possibility that the resin might take a color when exposedto sunlight, artificial lighting, or the like over a long period tobecome unusable in applications where transparency is especiallyrequired and in other applications.

It is preferred that the second polycarbonate resin of the inventionshould be one in which the molded object (thickness, 3 mm) formed fromthe resin has a light transmittance, as measured at a wavelength of 350nm, of 60% or higher. This light transmittance of the molded object ismore preferably 65% or higher, especially preferably 70% or higher. Whenthe light transmittance thereof at that wavelength is lower than 60%,there are the cases where this resin shows enhanced absorption and hasimpaired light resistance.

It is preferred that the second polycarbonate resin of the inventionshould be one in which the molded object (flat plate having a thicknessof 3 mm) formed from the resin has a light transmittance, as measured ata wavelength of 320 nm, of 30% or higher. This light transmittance ofthe molded object is more preferably 40% or higher, especiallypreferably 50% or higher. When the light transmittance thereof at thatwavelength is lower than 30%, there are the cases where the resin hasimpaired light resistance.

Furthermore, it is preferred that the second polycarbonate resin of theinvention should be one which, when molded into a flat plate having athickness of 3 mm and examined, has an L* value, as provided for byInternational Illumination Commission (CIE) and measured with respect totransmitted light, of generally 96.3 or higher. The L* value thereof ismore preferably 96.6 or higher, especially preferably 96.8 or higher.When the L* value thereof is less than 96.3, there are the cases wherethe resin has impaired light resistance.

Third Polycarbonate Resin

The third polycarbonate resin of the invention is a polycarbonate resinobtained by condensation-polymerizing at least one dihydroxy compoundincluding a dihydroxy compound which has the portion represented by thefollowing general formula (1) as part of the structure thereof with acarbonic diester represented by the following general formula (2) in thepresence of a catalyst which comprises one or more compounds of at leastone metal selected from the group consisting of lithium and the Group-2metals of the long-form periodic table, the polycarbonate resin having acontent of the metal compounds of 20 μmol or less in terms of metalamount per mole of the dihydroxy compound and containing an aromaticmonohydroxy compound in an amount of 700 weight ppm or less.

[Chem. 16]

CH₂—O  (1)

(The case where the portion represented by general formula (1) is partof —CH₂—O—H is excluded.)

(In general formula (2), A¹ and A² each independently are a substitutedor unsubstituted aliphatic group having 1-18 carbon atoms or asubstituted or unsubstituted aromatic group.)

The third polycarbonate resin of the invention is a polycarbonate resinobtained by condensation-polymerizing at least one dihydroxy compoundincluding the specific dihydroxy compound with a carbonic diester in thepresence of a specific amount of a specific catalyst. Since the contentof an aromatic monohydroxy compound therein has been regulated to avalue not larger than a specific amount, this polycarbonate resin hasexcellent light resistance, transparency, hue, heat resistance, thermalstability, and mechanical strength. Especially with respect to lightresistance, absorption in the visible-light region has conventionallyreceived attention. However, the present inventors have found that evenwhen resins show no absorption of visible light and appear to have nocolor when viewed through the human eyes, some of the resins take acolor upon exposure to sunlight, artificial lighting, or the like andothers do not. The invention has been thus achieved.

It is preferred that the third polycarbonate resin of the inventionshould be one which gives a molded object (thickness, 3 mm) that has alight transmittance, as measured at a wavelength of 350 nm, of 60% orhigher. This light transmittance of the molded object is more preferably65% or higher, especially preferably 70% or higher. When the lighttransmittance thereof at that wavelength is lower than 60%, there arethe cases where this resin shows enhanced absorption and has impairedlight resistance.

It is preferred that the third polycarbonate resin of the inventionshould be one which gives a molded object (thickness, 3 mm) that has alight transmittance, as measured at a wavelength of 320 nm, of 30% orhigher. This light transmittance of the molded object is more preferably40% or higher, especially preferably 50% or higher. When the lighttransmittance thereof at that wavelength is lower than 30%, there arethe cases where the resin has impaired light resistance.

It is preferred that the third polycarbonate resin of the inventionshould be one which gives a molded object (thickness, 3 mm) that has ayellowness index (YI) value, as measured with respect to transmittedlight in accordance with ASTM D1925-70, of 12 or less after having beenirradiated with light for 100 hours using a metal halide lamp in anenvironment of 63° C. and a relative humidity of 50% at an irradiancefor the wavelength range of 300-400 nm of 1.5 kW/m². The yellownessindex value thereof is more preferably 10 or less, especially preferably8 or less. When the yellowness index (YI) value thereof exceeds 12,there are the cases where the resin, even when colorless immediatelyafter molding, takes a color upon exposure to light includingultraviolet light.

It is preferred that the third polycarbonate resin of the inventionshould be one which gives a molded object (thickness, 3 mm) that, whenexamined without being subjected to the irradiation using a metal halidelamp as described above or the like, has a yellowness index value (i.e.,initial yellowness index value; referred to as initial YI value) asmeasured with respect to transmitted light of generally 10 or less. Theinitial YI value thereof is more preferably 7 or less, especiallypreferably 5 or less. The difference in yellowness index value betweenbefore and after the metal halide lamp irradiation is preferably 6 orless, more preferably 4 or less, especially preferably 3 or less, interms of absolute value.

When the initial yellowness index (YI) value thereof exceeds 10, thereis a tendency that this resin has impaired light resistance. In the casewhere the absolute value of the difference in yellowness index (YI)value between before and after the metal halide lamp irradiation exceeds6, there is a possibility that the resin might take a color when exposedto sunlight, artificial lighting, or the like over a long period tobecome unusable in applications where transparency is especiallyrequired and in other applications.

Furthermore, it is preferred that the third polycarbonate resin of theinvention should be one which, when examined as a molded object formedtherefrom (thickness, 3 mm), has an L* value, as provided for byInternational Illumination Commission (CIE) and measured with respect totransmitted light, of generally 96.3 or higher. The L* value thereof ismore preferably 96.6 or higher, especially preferably 96.8 or higher.When the L* value thereof is less than 96.3, there are the cases wherethe resin has impaired light resistance.

Any of the first to third polycarbonate resins described above(hereinafter also referred to simply as “polycarbonate resins of theinvention”) produces the effects of the invention. Such a polycarbonateresin can be produced, for example, by limiting the concentration ofspecific metals during polymerization, suitably selecting the kind andamount of catalyst, suitably selecting a polymerization temperature andpolymerization period, reducing the amount of compounds in the resinwhich have the ability to absorb ultraviolet rays, e.g., residual phenoland residual diphenyl carbonate, reducing the amount of anystarting-material monomer to be used which shows absorption in theultraviolet region, or reducing the amount of any starting material tobe used which contains an impurity that shows absorption in theultraviolet region. Especially important are the kind of catalyst andamount thereof, polymerization temperature, and polymerization period.

Processes for producing the polycarbonate resins of the invention willbe explained below in detail.

<Starting Materials> (Dihydroxy Compounds)

The polycarbonate resins of the invention at least contain structuralunits derived from a dihydroxy compound having the portion representedby the following general formula (1) as part of the structure thereof(hereinafter often referred to as “dihydroxy compound according to theinvention”). Namely, the dihydroxy compound according to the inventionis a dihydroxy compound which at least includes two hydroxyl groups andthe structural unit of the following general formula (1).

[Chem. 18]

CH₂—O  (1)

(The case where the portion represented by general formula (1) is partof —CH₂—O—H is excluded.)

The dihydroxy compound according to the invention is not particularlylimited as long as the compound has the portion represented by generalformula (1) as part of the structure thereof. Examples thereof includeoxyalkylene glycols such as diethylene glycol, triethylene glycol,tetraethylene glycol, and polyethylene glycol, compounds which have anaromatic group as a side chain and have, in the main chain, ether groupseach bonded to an aromatic group, such as9,9-bis(4-(2-hydroxyethoxy)phenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3-methylphenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3-tert-butylphenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethylphenyl)fluorene,9,9-bis(4-(2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl)fluorene, and9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl)fluorene, anhydroussugar alcohols represented by dihydroxy compounds represented by thefollowing general formula (4), and compounds having a cyclic etherstructure, such as the Spiro glycol represented by the following generalformula (5). Of these, diethylene glycol and triethylene glycol arepreferred from the standpoints of availability, handling, reactivityduring polymerization, and the hue of the polycarbonate resin to beobtained. Preferred from the standpoint of heat resistance are anhydroussugar alcohols represented by dihydroxy compounds represented by thefollowing general formula (4) and the compound having a cyclic etherstructure which is represented by the following general formula (5).

These compounds may be used alone or in combination of two or morethereof according to the performances required of the polycarbonateresin to be obtained.

Examples of the dihydroxy compounds represented by general formula (4)include isosorbide, isomannide, and isoidide, which are stereoisomers.These compounds may be used alone or in combination of two or morethereof.

From the standpoint of the light resistance of the polycarbonate resinsof the invention, it is preferred to use dihydroxy compounds having noaromatic ring structure among those dihydroxy compounds. Most preferredof these dihydroxy compounds is isosorbide from the standpoints ofavailability, ease of production, light resistance, optical properties,moldability, heat resistance, and carbon neutrality. Isosorbide isobtained by the dehydrating condensation of sorbitol, which is producedfrom various starches that are plant-derived abundant resources and areeasily available.

The polycarbonate resins of the invention may contain structural unitsderived from dihydroxy compounds other than the dihydroxy compoundaccording to the invention (hereinafter often referred to as “otherdihydroxy compounds”). Examples of the other dihydroxy compounds includealiphatic dihydroxy compounds such as ethylene glycol, 1,3-propanediol,1,2-propanediol, 1,4-butanediol, 1,3-butanediol, 1,2-butanediol,1,5-heptanediol, and 1,6-hexanediol, alicyclic dihydroxy compounds suchas 1,2-cyclohexanedimethanol, 1,3-cyclohexanedimethanol,1,4-cyclohexanedimethanol, tricyclodecanedimethanol,pentacyclopentadecanedimethanol, 2,6-decalindimethanol,1,5-decalindimethanol, 2,3-decalindimethanol, 2,3-norbornanedimethanol,2,5-norbornanedimethanol, and 1,3-adamantanedimethanol, and aromaticbisphenol compounds such as 2,2-bis(4-hydroxyphenyl)propane[=bisphenolA], 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane,2,2-bis(4-hydroxy-3,5-diethylphenyl)propane,2,2-bis(4-hydroxy-(3,5-diphenyl)phenyl)propane,2,2-bis(4-hydroxy-3,5-dibromophenyl)propane,2,2-bis(4-hydroxyphenyl)pentane, 2,4′-dihydroxydiphenylmethane,bis(4-hydroxyphenyl)methane, bis(4-hydroxy-5-nitrophenyl)methane,1,1-bis(4-hydroxyphenyl)ethane, 3,3-bis(4-hydroxyphenyl)pentane,1,1-bis(4-hydroxyphenyl)cyclohexane, bis(4-hydroxyphenyl)sulfone,2,4′-dihydroxydiphenyl sulfone, bis(4-hydroxyphenyl)sulfide,4,4′-dihydroxydiphenyl ether, 4,4′-dihydroxy-3,3′-dichlorodiphenylether, 9,9-bis(4-(2-hydroxyethoxy-2-methyl)phenyl)fluorene,9,9-bis(4-hydroxyphenyl)fluorene, and9,9-bis(4-hydroxy-2-methylphenyl)fluorene.

From the standpoint of the light resistance of the polycarbonate resins,it is preferred to use, among those compounds, at least one compoundselected from the group consisting of the dihydroxy compounds having noaromatic ring structure in the molecular structure thereof, i.e., thealiphatic dihydroxy compounds and the alicyclic dihydroxy compounds.Especially preferred of the aliphatic dihydroxy compounds are1,3-propanediol, 1,4-butanediol, and 1,6-hexanediol. Especiallypreferred of the alicyclic dihydroxy compounds are1,4-cyclohexanedimethanol and tricyclodecanedimethanol.

Use of such other dihydroxy compounds makes it possible to obtaineffects such as an improvement in the flexibility of the polycarbonateresins, improvement in the heat resistance thereof, improvement in themoldability thereof, etc. However, in the case where the content ofstructural units derived from other dihydroxy compounds is too high,this may result in a decrease in mechanical property and a decrease inheat resistance. Consequently, it is preferred that the proportion ofstructural units derived from the dihydroxy compound according to theinvention to structural units derived from all dihydroxy compoundsshould be 20% by mole or higher, preferably 30% by mole or higher,especially 50% by mole or higher.

When at least one of the dihydroxy compounds which are the dihydroxycompound according to the invention and other dihydroxy compounds has aboiling point of 300° C. or lower at atmospheric pressure, thisdihydroxy compound is apt to volatilize during the polymerizationreaction. The effects of the invention hence are enhanced in this case.When the boiling point thereof is 290° C. or lower, the effects arefurther enhanced.

The dihydroxy compound according to the invention may containstabilizers such as a reducing agent, antioxidant, free-oxygenscavenger, light stabilizer, antacid, pH stabilizer, and heatstabilizer. Since the dihydroxy compound according to the invention isapt to alter especially under acidic conditions, it is preferred thatthe dihydroxy compound should contain a basic stabilizer. Examples ofthe basic stabilizer include the hydroxides, carbonates, phosphates,phosphites, hypophosphites, borates, and fatty acid salts of Group-1 orGroup-2 metals of the long-form periodic table (Nomenclature ofInorganic Chemistry IUPAC Recommendations 2005). Examples thereoffurther include basic ammonium compounds such as tetramethylammoniumhydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide,tetrabutylammonium hydroxide, trimethylethylammonium hydroxide,trimethylbenzylammonium hydroxide, triethylphenylammonium hydroxide,triethylmethylammonium hydroxide, triethylbenzylammonium hydroxide,triethylphenylammonium hydroxide, tributylbenzylammonium hydroxide,tributylphenylammonium hydroxide, tetraphenylammonium hydroxide,benzyltriphenylammonium hydroxide, methyltriphenylammonium hydroxide,and butyltriphenylammonium hydroxide and amine compounds such as4-aminopyridine, 2-aminopyridine, N,N-dimethyl-4-aminopyridine,4-diethylaminopyridine, 2-hydroxypyridine, 2-methoxypyridine,4-methoxypyridine, 2-dimethylaminoimidazole, 2-methoxyimidazole,imidazole, 2-mercaptoimidazole, 2-methylimidazole, and aminoquinoline.Of these, the phosphates and phosphites of Na or K are preferred fromthe standpoints of the effect thereof and the ease of removal thereof bydistillation which will be described later. Especially preferred aredisodium hydrogen phosphate and disodium hydrogen phosphite.

There are no particular limitations on the content of those basicstabilizers in the dihydroxy compound according to the invention. In thecase where the content thereof is too low, there is a possibility thatthe effect of preventing the alteration of the dihydroxy compoundaccording to the invention might not be obtained. When the contentthereof is too high, there are the cases where the dihydroxy compoundaccording to the invention is altered. Consequently, the content ofthose basic stabilizers is generally 0.0001-1% by weight, preferably0.001-0.1% by weight, based on the dihydroxy compound according to theinvention.

When the dihydroxy compound according to the invention which containsthose basic stabilizers is used as a starting material for producing apolycarbonate resin, not only the basic stabilizers themselves serve asa polymerization catalyst to make it difficult to control polymerizationrate and quality, but also the presence of the basic stabilizers leadsto a deterioration in initial hue, resulting in molded articles havingimpaired light resistance. It is therefore preferred that the basicstabilizers should be removed with an ion-exchange resin or bydistillation or the like before the dihydroxy compound according to theinvention is used as a starting material for producing a polycarbonateresin.

In the case where the dihydroxy compound according to the invention is acompound having a cyclic ether structure, e.g., isosorbide, thisdihydroxy compound is apt to be gradually oxidized by oxygen. It istherefore preferred to handle the compound in an oxygen-free environmentduring storage or production in order to prevent decomposition caused byoxygen. It is important to use a free-oxygen scavenger or the like or tohandle the dihydroxy compound in a nitrogen atmosphere. There are thecases where isosorbide, upon oxidation, generates decomposition productsincluding formic acid. Since there is a possibility that the presence ofwater might accelerate generation of isosorbide decomposition products,it is also important to prevent water inclusion during storage. Forexample, in the case where isosorbide containing those decompositionproducts is used as a starting material for producing a polycarbonateresin, there is the possibility of resulting in a colored polycarbonateresin.

There also is a possibility that the decomposition products considerablydeteriorate the properties of the resin. In addition, there are thecases where the decomposition products affect the polymerizationreaction to make it impossible to obtain a polymer having a highmolecular weight. Use of such isosorbide hence is undesirable.

It is preferred to conduct purification by distillation in order toobtain the dihydroxy compound according to the invention which does notcontain the oxidative-decomposition products and to remove the basicstabilizers described above. The distillation in this case may be simpledistillation or continuous distillation, and is not particularlylimited. With respect to distillation conditions, it is preferred toconduct distillation at a reduced pressure in an inert gas atmospheresuch as argon or nitrogen. From the standpoint of inhibiting thermalalteration, it is preferred to conduct the distillation under theconditions of 250° C. or lower, preferably 200° C. or lower, especially180° C. or lower.

Through such purification by distillation, the content of formic acid inthe dihydroxy compound according to the invention is reduced to 20weight ppm or less, preferably 10 weight ppm or less, especiallypreferably 5 weight ppm or less. As a result, when dihydroxy compoundsincluding this dihydroxy compound according to the invention are used asa starting material for producing a polycarbonate resin,polymerizability is not impaired and a polycarbonate resin having anexcellent hue and excellent thermal stability can be produced. Thecontent of formic acid is determined by ion chromatography.

(Carbonic Diester)

The polycarbonate resins of the invention can be obtained using at leastone dihydroxy compound including the dihydroxy compound according to theinvention described above and a carbonic diester as starting materials,by condensation-polymerizing the starting materials by means of atransesterification reaction.

Examples of the carbonic diester to be used usually include compoundsrepresented by the following general formula (2). One of these carbonicdiesters may be used alone, or a mixture of two or more thereof may beused.

(In general formula (2), A¹ and A² each independently are a substitutedor unsubstituted aliphatic group having 1-18 carbon atoms or asubstituted or unsubstituted aromatic group.)

Examples of the carbonic diesters represented by general formula (2)include diphenyl carbonate, substituted diphenyl carbonates, e.g.,ditolyl carbonate, dimethyl carbonate, diethyl carbonate, and di-t-butylcarbonate. Preferred are diphenyl carbonate and substituted diphenylcarbonates. Especially preferred is diphenyl carbonate (hereinafteroften abbreviated to “DPC”). Incidentally, there are the cases wherecarbonic diesters contain impurities such as chloride ions and where theimpurities inhibit the polymerization reaction and impair the hue of thepolycarbonate resin to be obtained. It is therefore preferred that acarbonic diester which has been purified by, for example, distillationshould be used according to need.

(Transesterification Reaction Catalyst)

The polycarbonate resins of the invention each are produced bysubjecting at least one dihydroxy compound including the dihydroxycompound according to the invention as described above and the carbonicdiester to a transesterification reaction. More specifically, thepolycarbonate resin is obtained by subjecting the starting materials totransesterification and removing the by-product monohydroxy compound,etc. from the system. In this case, polycondensation is usuallyconducted by means of a transesterification reaction in the presence ofa transesterification reaction catalyst.

The transesterification reaction catalyst (hereinafter often referred tosimply as “catalyst” or “polymerization catalyst”) can affect lighttransmittance as measured especially at a wavelength of 350 nm andyellowness index value.

The catalyst to be used is not limited so long as the catalyst enablesthe polycarbonate resin produced therewith to satisfy, in particular,light resistance among light resistance, transparency, hue, heatresistance, thermal stability, and mechanical strength, that is, thecatalyst enables the polycarbonate resin to have a given value of lighttransmittance as measured at a wavelength of 350 nm and a givenyellowness index value. Examples thereof include compounds of metalsbelonging to the Group 1 or Group 2 of the long-form periodic table(hereinafter referred to simply as “Group 1” or “Group 2”) and basiccompounds such as basic boron compounds, basic phosphorus compounds,basic ammonium compounds, and amine compounds. It is preferred to use aGroup-1 metal compound and/or a Group-2 metal compound.

It is possible to use a basic compound such as a basic boron compound,basic phosphorus compound, basic ammonium compound, or amine compound asan auxiliary together with a Group-1 metal compound and/or a Group-2metal compound. It is, however, especially preferred to use a Group-1metal compound and/or a Group-2 metal compound only.

With respect to the form of the Group-1 metal compound and/or Group-2metal compound, the compound is used usually in the form of a hydroxideor a salt such as carbonate, carboxylate, or phenolate. However,hydroxides, carbonates, and acetates are preferred from the standpointsof availability and handleability, and acetates are preferred from thestandpoints of hue and activity in polymerization.

Examples of the Group-1 metal compound include sodium hydroxide,potassium hydroxide, lithium hydroxide, cesium hydroxide, sodiumhydrogen carbonate, potassium hydrogen carbonate, lithium hydrogencarbonate, cesium hydrogen carbonate, sodium carbonate, potassiumcarbonate, lithium carbonate, cesium carbonate, sodium acetate,potassium acetate, lithium acetate, cesium acetate, sodium stearate,potassium stearate, lithium stearate, cesium stearate, sodium boronhydride, potassium boron hydride, lithium boron hydride, cesium boronhydride, phenylated boron-sodium compounds, phenylated boron-potassiumcompounds, phenylated boron-lithium compounds, phenylated boron-cesiumcompounds, sodium benzoate, potassium benzoate, lithium benzoate, cesiumbenzoate, disodium hydrogen phosphate, dipotassium hydrogen phosphate,dilithium hydrogen phosphate, dicesium hydrogen phosphate, disodiumphenyl phosphate, dipotassium phenyl phosphate, dilithium phenylphosphate, dicesium phenyl phosphate, alcoholates or phenolates ofsodium, potassium, lithium, and cesium, and the disodium salt,dipotassium salt, dilithium salt, and dicesium salt of bisphenol A.Preferred of these are the lithium compounds.

Examples of the Group-2 metal compound include calcium hydroxide, bariumhydroxide, magnesium hydroxide, strontium hydroxide, calcium hydrogencarbonate, barium hydrogen carbonate, magnesium hydrogen carbonate,strontium hydrogen carbonate, calcium carbonate, barium carbonate,magnesium carbonate, strontium carbonate, calcium acetate, bariumacetate, magnesium acetate, strontium acetate, calcium stearate, bariumstearate, magnesium stearate, and strontium stearate. Preferred of theseare the magnesium compounds, the calcium compounds, and the bariumcompounds. From the standpoints of activity in polymerization and thehue of the polycarbonate resin to be obtained, at least one metalcompound selected from the magnesium compounds and the calcium compoundsis more preferred, and the calcium compounds are most preferred.

Examples of the basic boron compounds include the sodium salts,potassium salts, lithium salts, calcium salts, barium salts, magnesiumsalts, or strontium salts of tetramethylboron, tetraethylboron,tetrapropylboron, tetrabutylboron, trimethylethylboron,trimethylbenzylboron, trimethylphenylboron, triethylmethylboron,triethylbenzylboron, triethylphenylboron, tributylbenzylboron,tributylphenylboron, tetraphenylboron, benzyltriphenylboron,methyltriphenylboron, and butyltriphenylboron.

Examples of the basic phosphorus compounds include triethylphosphine,tri-n-propylphosphine, triisopropylphosphine, tri-n-butylphosphine,triphenylphosphine, tributylphosphine, and quaternary phosphonium salts.

Examples of the basic ammonium compounds include tetramethylammoniumhydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide,tetrabutylammonium hydroxide, trimethylethylammonium hydroxide,trimethylbenzylammonium hydroxide, triethylphenylammonium hydroxide,triethylmethylammonium hydroxide, triethylbenzylammonium hydroxide,triethylphenylammonium hydroxide, tributylbenzylammonium hydroxide,tributylphenylammonium hydroxide, tetraphenylammonium hydroxide,benzyltriphenylammonium hydroxide, methyltriphenylammonium hydroxide,and butyltriphenylammonium hydroxide.

Examples of the amine compounds include 4-aminopyridine,2-aminopyridine, N,N-dimethyl-4-aminopyridine, 4-diethylaminopyridine,2-hydroxypyridine, 2-methoxypyridine, 4-methoxypyridine,2-dimethylaminoimidazole, 2-methoxyimidazole, imidazole,2-mercaptoimidazole, 2-methylimidazole, and aminoquinoline.

The amount of the polymerization catalyst to be used is usuallypreferably 0.1-300 μmol, more preferably 0.5-100 μmol, per mole of alldihydroxy compounds subjected to the polymerization. Especially in thecase where use is made of one or more compounds containing at least onemetal selected from the group consisting of lithium and the Group-2metals of the long-form periodic table, in particular, in the case whereat least one metal compound selected from magnesium compounds andcalcium compounds is used, the amount of this catalyst is generally 0.1μmol or more, preferably 0.5 μmol or more, especially preferably 0.7μmol or more, in terms of metal amount per mole of all dihydroxycompounds. The suitable upper limit thereof is generally 20 μmol,preferably 10 μmol, more preferably 3 μmol, especially preferably 1.5μmol, in particular 1.0 μmol.

When the amount of the catalyst is too small, there are the cases wherethe rate of polymerization is too low. As a result, a higherpolymerization temperature must be used in order to obtain apolycarbonate resin having a desired molecular weight, and thepolycarbonate resin thus obtained has an impaired hue and impaired lightresistance. In addition, there is a possibility that an unreactedstarting material might volatilize during the polymerization to changethe molar proportions of the at least one dihydroxy compound includingthe dihydroxy compound according to the invention and of the carbonicdiester and a desired molecular weight might hence be not reached. Onthe other hand, in the case where the polymerization catalyst is used intoo large an amount, there is a possibility that the resultantpolycarbonate resin might have an impaired hue and impaired lightresistance.

There is a possibility that when Group-1 metals, especially sodium,potassium, and cesium, in particular, lithium, sodium, potassium, andcesium, are contained in a polycarbonate resin in a large amount, thesemetals might adversely affect the hue. These metals do not come onlyfrom the catalyst used but may come from starting materials and thereactor. Consequently, the total amount of compounds of those metals inthe polycarbonate resin is usually preferably 1 weight ppm or less, morepreferably 0.8 weight ppm or less, even more preferably 0.7 weight ppmor less, in terms of metal amount.

The content of metals in a polycarbonate resin can be determined byrecovering the metals contained in the polycarbonate resin by atechnique such as wet ashing and then determining the amount of themetals using a technique such as atomic emission, atomic absorption, orinductively coupled plasma (ICP) spectroscopy.

In the case where diphenyl carbonate or a substituted diphenylcarbonate, e.g., ditolyl carbonate, is used as a carbonic diesterrepresented by general formula (2) to produce a polycarbonate resin ofthe invention, phenol or a substituted phenol generates as a by-productand unavoidably remains in the polycarbonate resin. However, sincephenol and the substituted phenol also have an aromatic ring, there arethe cases where not only these compounds absorb ultraviolet rays toserve as a factor contributing to a deterioration in light resistancebut also the compounds are causative of an odor during molding. After anordinary batch reaction, the polycarbonate resin contains an aromaticmonohydroxy compound having an aromatic ring, e.g., by-product phenol,in an amount of 1,000 weight ppm or more. From the standpoints of lightresistance and odor diminution, it is preferred to reduce the content ofthe aromatic monohydroxy compound to preferably 700 weight ppm or less,more preferably 500 weight ppm or less, especially 300 weight ppm orless, using a horizontal reactor having excellent volatilizingperformance or using an extruder having a vacuum vent. It is, however,noted that it is difficult to industrially completely remove thearomatic monohydroxy compound, and the lower limit of the contentthereof is generally 1 weight ppm.

Those aromatic monohydroxy compounds may, of course, have substituents,depending on the starting materials used. For example, the compounds mayhave an alkyl group having up to 5 carbon atoms or the like.

When the number of moles of the H bonded to the aromatic rings of eachpolycarbonate resin of the invention is expressed by A and the number ofmoles of the H bonded to the part other than the aromatic rings isexpressed by B, then the proportion of the number of moles of the Hbonded to the aromatic rings to the number of moles of all H isexpressed by A/(A+B). Since there is a possibility that the aromaticrings, which have ultraviolet-absorbing ability, might affect lightresistance as stated above, it is preferred that A/(A+B) should be 0.1or less, more preferably 0.05 or less, even more preferably 0.02 orless, especially preferably 0.01 or less. The value of A/(A+B) can bedetermined by ¹H NMR spectroscopy.

<First Production Process>

Although the polycarbonate resins of the invention each is obtained bycondensation-polymerizing one or more dihydroxy compounds including thedihydroxy compound according to the invention with the carbonic diesterby means of a transesterification reaction, it is preferred to evenlymix the starting materials, i.e., the dihydroxy compounds and thecarbonic diester, prior to the transesterification reaction.

The temperature at which the starting materials are mixed together isgenerally 80° C. or higher, preferably 90° C. or higher, and the upperlimit thereof is generally 250° C. or lower, preferably 200° C. orlower, more preferably 150° C. or lower. Especially suitable is atemperature of 100-120° C. In the case where the mixing temperature istoo low, there is the possibility of resulting in too low a dissolutionrate or in insufficient solubility. In addition, there are often thecases where troubles such as solidification arise. When the mixingtemperature is too high, there are the cases where the dihydroxycompounds deteriorate thermally. There is hence a possibility that thepolycarbonate resin obtained has an impaired hue and this adverselyaffects light resistance.

It is preferred that an operation for mixing the dihydroxy compoundsincluding the dihydroxy compound according to the invention and thecarbonic diester, which are starting materials for a polycarbonate resinof the invention, should be conducted in an atmosphere having an oxygenconcentration of 10 vol % or less, typically 0.0001-10 vol %. From thestandpoint of preventing hue deterioration, it is preferred to conductthe operation in an atmosphere having an oxygen concentration of, inparticular, 0.0001-5 vol %, especially 0.0001-1 vol %.

It is preferred that for obtaining a polycarbonate resin of theinvention, the carbonic diester should be used in such an amount thatthe molar proportion thereof to the dihydroxy compounds to be subjectedto the reaction, which include the dihydroxy compound according to theinvention, is 0.90-1.20. The molar proportion thereof is more preferably0.95-1.10.

In the case where the molar proportion thereof is too low, there is apossibility that the polycarbonate resin produced might have anincreased amount of terminal hydroxyl groups and this might impair thethermal stability of the polymer and cause the polymer to take a colorupon molding. There also is a possibility that the rate oftransesterification reaction might decrease or a desired high-molecularpolymer might not be obtained.

On the other hand, when the molar proportion thereof is too high, thereare the cases where the rate of transesterification reaction decreasesor it is difficult to produce a polycarbonate having a desired molecularweight. The decrease in the rate of transesterification reactionenhances heat history during the polymerization reaction, resulting in apossibility that the enhanced heat history might impair the hue andlight resistance of the polycarbonate resin obtained.

Furthermore, when the molar proportion of the carbonic diester to thedihydroxy compounds including the dihydroxy compound according to theinvention is too high, there are the cases where the polycarbonate resinobtained has an increased content of the residual carbonic diester andthe residual carbonic diester absorbs ultraviolet rays to impair thelight resistance of the polycarbonate resin. The concentration of thecarbonic diester remaining in each polycarbonate resin of the inventionis preferably 200 weight ppm or less, more preferably 100 weight ppm orless, even more preferably 60 weight ppm or less, especially preferably30 weight ppm or less. Actually, some polycarbonate resins containunreacted carbonic diesters. A lower limit of the concentration thereofis generally 1 weight ppm.

In the invention, a process in which the dihydroxy compounds arecondensation-polymerized with the carbonic diester is conducted in thepresence of the catalyst described above usually in multiple stagesusing a plurality of reactors. The mode of reaction operation may be anyof the batch type, the continuous type, and a combination of the batchtype and the continuous type. It is, however, preferred that the processshould be continuous. The reasons for this are, for example, that it iseasy to set more preferred reaction conditions for each reaction stageand that it is easy to diminish the unreacted monomers and by-productsof the reaction.

It is preferred that in the initial stage of the polymerization, thepolymerization should be conducted at a relatively low temperature andunder relatively low vacuum to obtain a prepolymer, and that in the latestage of the polymerization, the polymerization should be conducted at arelatively high temperature under relatively high vacuum to heighten themolecular weight to a given value. It is, however, important from thestandpoints of hue and light resistance that a jacket temperature, aninternal temperature, and an internal pressure of the system should besuitably selected for each molecular-weight stage. For example, in thecase where either temperature or pressure is too speedily changed beforethe polymerization reaction reaches a given value, an unreacted monomeris distilled off to change the molar ratio of the dihydroxy compounds tothe carbonic diester. This may result in a decrease in polymerizationrate or make it impossible to obtain a polymer having a given molecularweight or having given end groups. There hence is a possibility that theobjects of the invention cannot finally be accomplished.

To provide a polymerization reactor with a reflux condenser is effectivefor inhibiting the monomers from being distilled off. This effect ishigh especially in the reactor for the initial stage of polymerization,in which the amount of unreacted monomer ingredients is large. Thetemperature of the coolant which is being introduced into the refluxcondenser can be suitably selected according to the monomers used.However, the temperature of the coolant being introduced into the refluxcondenser, as measured at the inlet of the reflux condenser, isgenerally 45-180° C., preferably 80-150° C., especially preferably100-130° C. In the case where the temperature of the coolant beingintroduced into the reflux condenser is too high, the amount of themonomers being refluxed decreases, resulting in a decrease in the effectof the refluxing. When the temperature thereof is too low, there are thecases where the efficiency of the removal by distillation of themonohydroxy compound to be removed by distillation decreases. As thecoolant, use may be made of hot water, steam, a heat-medium oil, or thelike. It is preferred to use steam or a heat-medium oil.

The selection of the kind and amount of a catalyst described above isimportant for maintaining a suitable polymerization rate and inhibitingthe monomers from being distilled off and for simultaneously enablingthe finally obtained polycarbonate resin to have intact properties suchas hue, thermal stability, and light resistance.

It is preferred that each polycarbonate resin of the invention should beproduced by polymerizing the starting materials in multiple stages usinga catalyst and a plurality of reactors. The reasons why thepolymerization is conducted in a plurality of reactors are that in theinitial stage of the polymerization reaction, since the monomers arecontained in a large amount in the liquid reaction mixture, it isimportant that the monomers should be inhibited from volatilizing offwhile maintaining a necessary polymerization rate, and that in the latestage of the polymerization reaction, it is important to sufficientlyremove by distillation the by-product monohydroxy compound in order toshift the equilibrium to the polymerization side. For thus settingdifferent sets of polymerization reaction conditions, it is preferred touse a plurality of polymerization reactors arranged serially, from thestandpoint of production efficiency.

The number of reactors to be used in the process of the invention is notlimited so long as the number thereof is at least 2 as described above.From the standpoints of production efficiency, etc., the number thereofis 3 or more, preferably 3-5, especially preferably 4.

In the invention, the process may be conducted in various manners solong as two or more reactors are used. For example, a plurality ofreaction stages differing in conditions are formed in any of thereactors, or the temperature and the pressure may be continuouslychanged in any of the reactors.

In the invention, the polymerization catalyst can be introduced into astarting-material preparation tank or a starting-material storage tank,or can be introduced directly into a polymerization vessel. However,from the standpoints of stability of feeding and polymerization control,a catalyst supply line is disposed somewhere in a starting-material linebefore a polymerization vessel, and the catalyst is supplied preferablyin the form of an aqueous solution.

With respect to polymerization reaction temperature, too lowtemperatures result in a decrease in productivity and cause the productto undergo an enhanced heat history. Too high temperatures not onlyresult in monomer volatilization but also result in the possibility ofenhancing degradation and coloring of the polycarbonate resin.

Specifically, the reaction in the first stage may be conducted at atemperature of 140-270° C., preferably 180-240° C., more preferably200-230° C., in terms of the maximum internal temperature of thepolymerization reactor, and a pressure of 110-1 kPa, preferably 70-5kPa, more preferably 30-10 kPa (absolute pressure) for 0.1-10 hours,preferably 0.5-3 hours, while the monohydroxy compound which generatesis being removed from the reaction system by distillation.

In the second and any succeeding stages, the pressure of the reactionsystem is gradually lowered from the pressure used in the first stage,and the polymerization is conducted while the monohydroxy compound whichgenerates is being continuously removed from the reaction system.Finally, the pressure (absolute pressure) of the reaction system islowered to 200 Pa or below. The second and any succeeding stages arethus conducted at a maximum internal temperature of 210-270° C.,preferably 220-250° C., for a period of generally 0.1-10 hours,preferably 1-6 hours, especially preferably 0.5-3 hours.

Especially from the standpoints of inhibiting a polycarbonate resin fromtaking a color or deteriorating thermally and of thereby obtaining apolycarbonate resin having a satisfactory hue and satisfactory lightresistance, it is preferred that the maximum internal temperature in allreaction stages should be lower than 250° C., in particular 225-245° C.From the standpoints of inhibiting the rate of polymerization fromdecreasing in the latter half of the polymerization reaction and ofthereby minimizing the deterioration caused by heat history, it ispreferred to use, in the final stage of the polymerization, a horizontalreactor having excellent plug flow characteristics and interface renewalcharacteristics.

In the case where the polymerization is conducted at too high atemperature or for too long a period in order to obtain a polycarbonateresin having a given molecular weight, there is a tendency that theresultant polycarbonate resin has a reduced ultraviolet transmittanceand an increased YI value.

From the standpoint of effective utilization of resources, it ispreferred that the monohydroxy compound which generated as a by-productshould be reused as a starting material for diphenyl carbonate,bisphenol A, or the like after purified according to need.

<Second Production Process>

A second process for polycarbonate resin production according to theinvention is a process for producing a polycarbonate resin using acarbonic diester and at least one dihydroxy compound asstarting-material monomers and a catalyst, by condensation-polymerizingthe starting-material monomers by means of a transesterificationreaction using a plurality of reactors in multiple stages, and ischaracterized in that

the dihydroxy compound comprises a dihydroxy compound having the portionrepresented by the following general formula (1) as part of thestructure thereof,

at least one of the reactors from which the monohydroxy compoundgenerated as a by-product of the transesterification reaction isdistilled off in an amount at least 20% of a theoretical distillationremoval amount is a reactor which has a capacity of 20 L or more andwhich is equipped with a heating means for heating the reactor by meansof a heating medium and further equipped with a reflux condenser, thedifference between the temperature of the heating medium and thetemperature of the liquid reaction mixture present in the reactor being5° C. or more, and

the total amount of the monomers which are distilled off in all reactionstages is up to 10% by weight of the sum of the starting-materialmonomers.

[Chem. 22]

CH₂—O  (1)

(The case where the portion represented by general formula (1) is partof —CH₂—O—H is excluded.)

In the second production process, at least one of the reactors fromwhich the monohydroxy compound is distilled off in an amount at least20% of a theoretical distillation removal amount thereof has a capacityof 20 L or more, preferably 30 L or more. The larger the capacity of thereactor, the higher the effects of the invention.

In the second production process of the invention, the carbonic diesterand the dihydroxy compound are subjected to polycondensation (oftenreferred to simply as polymerization) by means of a transesterificationreaction using a plurality of reactors in multiple stages in thepresence of the catalyst described above. In this polymerizationreaction, a monohydroxy compound (for example, phenol when diphenylcarbonate was used as the carbonic diester) generates as a by-product ofthe reaction. The polymerization is conducted while removing bydistillation the by-product monohydroxy compound from the system.However, in the initial stage of the polymerization, the amount of themonohydroxy compound which generates as a by-product per unit period islarge, and the removal of the monohydroxy compound deprives the systemof a large amount of latent heat of vaporization. Consequently, in theinvention, at least one of the reactors from which the monohydroxycompound is distilled off in an amount at least 20% of a theoreticaldistillation removal amount thereof is a reactor which is equipped witha heating means for heating the reactor by means of a heating medium,and the temperature of the heating medium which is being introduced isregulated so as to be higher than the temperature of the liquid reactionmixture present in the reactor (hereinafter often referred to as“internal temperature”), i.e., so as to result in a difference betweenthese temperatures of at least 5° C. [(heating mediumtemperature)>(internal temperature)].

The theoretical distillation removal amount of the monohydroxy compoundin the invention is the number of moles which is two times the number ofmoles of the carbonic diester used as a starting material. In the caseof a batch reaction, the term “reactor from which the monohydroxycompound is distilled off in an amount at least 20% of the theoreticaldistillation removal amount” means a reactor in which the total amountof the monohydroxy compound that is distilled off from the one reactoris at least 20% of the theoretical distillation removal amountcalculated from the amount of the carbonic diester compound that was fedat first as a starting material. In the case of a continuous reaction,that term means a reactor in which the amount of the monohydroxycompound that is distilled off from the one reactor per unit period isat least 20% of the theoretical distillation removal amount calculatedfrom the amount of the carbonic diester that is fed as a startingmaterial per unit period.

Examples of the heating means for heating the reactor by means of aheating medium include a jacket type disposed around the reactor(throughout the whole periphery or in part thereof) (hereinafter oftenreferred to simply as “heating medium jacket”), a type which includes aninternal coil disposed in the reactor, and a heat exchanger typedisposed outside the reactor. However, it is preferred that the heatingmeans should be a heating medium jacket. In the case of using a heatingmedium jacket, to further dispose an internal coil inside the reactorand thereby heat the reaction mixture also from the inside of thereactor and increase the area of heat-transfer surface for heating iseffective for avoiding the necessity of excessively elevating thetemperature of the heating medium within the jacket.

When the difference between the temperature of the heating medium andthe temperature of the liquid reaction mixture is less than 5° C., thereare the cases where the reactor has an impaired heat balance and thetemperature of the liquid reaction mixture cannot be regulated to agiven temperature. Especially in the case of larger reactors whichemploy, for example, a heating medium jacket as a heating means, thearea of the heat-transfer surface of the heating medium jacket tends tobe small as compared with the capacities of the reactors. It istherefore desirable that the difference between the temperature of theheating medium and the temperature of the liquid reaction mixture shouldbe large. The difference therebetween is preferably 10° C. or more,especially preferably 15° C. or more.

Conversely, in the case where the difference between the temperature ofthe heating medium and the temperature of the liquid reaction mixture istoo large, not only a starting-material monomer is distilled off in anincreased amount but also the contents undergo a severer thermaldeterioration. Consequently, the difference therebetween is preferably80° C. or less, more preferably 40° C. or less, especially preferably30° C. or less.

The temperature of the heating medium to be introduced may be suitablydetermined according to the desired temperature of the liquid reactionmixture. However, in the case where the temperature of the heatingmedium is too high, a starting-material monomer is distilled off in toolarge an amount. Consequently, the maximum temperature is preferablylower than 265° C., more preferably lower than 260° C., especiallypreferably lower than 255° C.

With respect to an operation for regulating the temperature of theheating medium so as to be higher by at least 5° C. than the temperatureof the liquid reaction mixture, use may be made of a method in which thetemperature of the heating medium is always kept higher by at least 5°C. throughout the period of the reaction within the one reactor.Alternatively, use may be made of a method in which the temperatureregulation is conducted only during the period in which the monohydroxycompound is distilled off considerably. In general, the former method isused in continuous reactions, while the latter method is used in batchreactions.

In the invention, the term “temperature of the heating medium” means thetemperature measured before the heating medium is introduced into theheating means. For example, in the case where the heating means is aheating medium jacket, that term means the temperature of the heatingmedium measured before the heating medium is introduced into the heatingmedium jacket disposed around the reactor (throughout the wholeperiphery or in part thereof). In the invention, the term “temperatureof the liquid reaction mixture” means the temperature of the liquidreaction mixture measured with a measuring device, e.g., a thermocouple.

The internal temperature of at least one of the reactors from which themonohydroxy compound generated as a by-product of the polymerizationreaction is distilled off in an amount at least 20% of a theoreticaldistillation removal amount, in the invention, is usually preferably140-270° C., more preferably 180-240° C., even more preferably 200-230°C. In the case where the internal temperature thereof is too high, notonly a starting-material monomer is distilled off in an increased amountbut also thermal deterioration is enhanced. In the case where theinternal temperature thereof is too low, the rate of reaction is low,resulting in a decrease in production efficiency.

In the invention, at least one of the reactors from which themonohydroxy compound is distilled off in an amount at least 20% of atheoretical distillation removal amount thereof is equipped with areflux condenser in order to inhibit the monomers from being distilledoff.

The temperature of the coolant to be introduced into the refluxcondenser is preferably 45-180° C., more preferably 80-150° C.,especially preferably 100-130° C., in terms of temperature as measuredat the inlet of the reflux condenser. When the coolant has too high atemperature, there are the cases where the amount of the monomers beingrefluxed decreases, resulting in a decrease in the effect of therefluxing.

Conversely, when the temperature thereof is too low, there are the caseswhere the efficiency of the removal by distillation of the monohydroxycompound to be removed by distillation decreases. As the coolant, usemay be made of hot water, steam, a heat-medium oil, or the like. It ispreferred to use steam or a heat-medium oil.

It is preferred that reactors from which the monohydroxy compound isdistilled off in an amount at least 10% of a theoretical distillationremoval amount thereof should also be equipped with a reflux condenserin order to inhibit the monomers from being distilled off.

It is important in the second production process of the invention thatthe total amount of the monomers which are distilled off in all reactionstages should be up to 10% by weight of the sum of the starting-materialmonomers.

The term “total amount of the monomers which are distilled off in allreaction stages” (hereinafter sometimes referred to as “amount of themonomers distilled off”) means the total amount of all monomers whichwere distilled off during the period from initiation to termination ofthe transesterification reaction.

In the case where the amount of the monomers distilled off exceeds 10%by weight of the sum of the starting-material monomers, this not onlyresults in a decrease in material unit but also poses a problem that itbecomes difficult to regulate the concentration of end groups, whichaffects quality, to a given value. In addition, in the case where aplurality of dihydroxy compounds are used, there is a possibility thatthe molar proportions of the dihydroxy compounds used might changeduring the polymerization, making it impossible to obtain apolycarbonate resin having a desired molecular weight and composition.

The amount of the monomers distilled off is preferably 5% by weight orless, more preferably 3% by weight or less, especially preferably 2% byweight or less, based on the sum of the starting-material monomers.

Smaller amounts of the monomers distilled off bring about a largerimprovement in material unit. However, smaller amounts thereofnecessitate an excessive reduction in internal temperature or heatingmedium temperature, an excessively elevated pressure, an increase incatalyst amount, or prolongation of the polymerization period, resultingin a decrease in polycarbonate resin production efficiency and adeterioration in quality. Consequently, the lower limit thereof isgenerally 0.2% by weight, preferably 0.4% by weight, more preferably0.6% by weight.

The amount of monomers distilled off which has been specified in theinvention can be attained by suitably selecting the kind and amount of acatalyst, temperature of the liquid reaction mixture, temperature of theheating medium, reaction pressure, residence time, refluxing conditions,etc. as described above.

For example, a prepolymer is obtained in the initial stage of thepolymerization at a relatively low temperature under relatively lowvacuum, and the molecular weight thereof is increased to a given valueat a relatively high temperature under relatively high vacuum in thelate stage of the polymerization. It is, however, important that atemperature of the heating medium, an internal temperature, and aninternal pressure of the reaction system should be suitably selected foreach molecular-weight stage. For example, in the case where eithertemperature or pressure is too speedily changed before thepolymerization reaction reaches a given value, an unreacted monomer isdistilled off to change the molar ratio of the dihydroxy compounds tothe carbonic diester. There hence is a possibility that thepolymerization rate might decrease or it might be impossible to obtain apolymer having a given molecular weight or having given end groups.

The selection of the kind and amount of a catalyst described above isalso important for maintaining a suitable polymerization rate andinhibiting the monomers from being distilled off and for simultaneouslyenabling the finally obtained polycarbonate resin to have intactproperties such as hue, thermal stability, and light resistance.

In the second production process of the invention, a polycarbonate resinis produced by polymerizing the starting materials in multiple stagesusing a catalyst and a plurality of reactors. The reasons why thepolymerization is conducted in a plurality of reactors are that in theinitial stage of the polymerization reaction, since the monomers arecontained in a large amount in the liquid reaction mixture, it isimportant that the monomers should be inhibited from volatilizing offwhile maintaining a necessary polymerization rate, and that in the latestage of the polymerization reaction, it is important to sufficientlyremove by distillation the by-product monohydroxy compound in order toshift the equilibrium to the polymerization side. For thus settingdifferent sets of polymerization reaction conditions, it is preferred touse a plurality of polymerization reactors arranged serially, from thestandpoint of production efficiency. With respect to the mode ofreaction operation, it is preferred to employ the continuous type inwhich those stages are continuously performed.

The number of reactors to be used in the process of the invention is notlimited so long as the number thereof is at least 2 as described above.From the standpoints of production efficiency, etc., the number thereofis 3 or more, preferably 3-5, especially preferably 4.

In the invention, the process may be conducted in various manners solong as two or more reactors are used. For example, a plurality ofreaction stages differing in conditions are formed in any of thereactors to change the temperature and the pressure in stages orcontinuously.

Examples thereof include: the case in which two reactors are used toconduct polymerization in two stages using different sets of reactionconditions for the reactors; and the case in which two reactors are usedin such a manner that two reaction stages differing in conditions areconducted in the first reactor and the second reactor is operated underone set of reaction conditions, thereby performing polymerization inthree stages.

In the invention, the catalyst can be introduced into astarting-material preparation tank or a starting-material storage tank,or can be introduced directly into a reactor. However, from thestandpoints of the stability of feeding and polymerization control, acatalyst supply line is disposed somewhere in a starting-material linebefore a reactor, and the catalyst is supplied preferably in the form ofan aqueous solution.

With respect to transesterification reaction temperature, too lowtemperatures result in a decrease in productivity and cause the productto undergo an enhanced heat history. Too high temperatures not onlyresult in monomer volatilization but also result in the possibility ofenhancing degradation and coloring of the polycarbonate resin.

With respect to the internal temperature of at least one of the reactorsfrom which the by-product monohydroxy compound is distilled off in anamount at least 20% of a theoretical distillation removal amount, themaximum temperature thereof is 140-270° C., preferably 180-240° C., morepreferably 200-230° C., as stated above. Other conditions include apressure of generally 110-1 kPa, preferably 70-5 kPa, more preferably30-10 kPa (absolute pressure), and a period of generally 0.1-10 hours,preferably 0.5-3 hours. The transesterification reaction is conductedunder such conditions while the monohydroxy compound which generates isbeing removed from the reaction system by distillation.

In the second and any succeeding stages, the pressure of the reactionsystem is gradually lowered from the pressure used in the first stage,and the polymerization is conducted while the monohydroxy compound whichgenerates is being continuously removed from the reaction system.Finally, the pressure (absolute pressure) of the reaction system islowered to generally 1,000 Pa or below, preferably 200 Pa or below. Thesecond and any succeeding stages are thus conducted at a maximuminternal temperature of 210-270° C., preferably 220-250° C.

Especially from the standpoints of inhibiting the polycarbonate resinfrom taking a color or deteriorating thermally and of regulating theamount of monomers distilled off to up to 10% by weight of the sum ofthe starting-material monomers, it is preferred that the maximuminternal temperature in all reaction stages should be lower than 250°C., in particular 225-245° C. In this process of the invention, it ispreferred from the standpoint of effective utilization of resources thatthe monohydroxy compound which generated as a by-product should bereused as a starting material for a carbonic diester, bisphenolcompound, or the like after purified according to need.

<Third Production Process>

A third process for polycarbonate resin production according to theinvention is a process for producing a polycarbonate resin using acarbonic diester and at least one dihydroxy compound asstarting-material monomers and a catalyst, by condensation-polymerizingthe starting-material monomers by means of a transesterificationreaction using a plurality of reactors in multiple stages, and ischaracterized in that

the dihydroxy compound comprises a plurality of dihydroxy compounds, atleast one of which is a dihydroxy compound having the portionrepresented by the following general formula (1) as part of thestructure thereof,

at least one of the reactors from which the monohydroxy compoundgenerated as a by-product of the transesterification reaction isdistilled off in an amount at least 20% of a theoretical distillationremoval amount is a reactor which has a capacity of 20 L or more andwhich is equipped with a heating means for heating the reactor by meansof a heating medium and further equipped with a reflux condenser, thedifference between the temperature of the heating medium and thetemperature of the liquid reaction mixture present in the reactor being5° C. or more, and

the value obtained by dividing the difference between the molarproportion in percentage of each dihydroxy compound which is being fedas a starting material to the reactors and the molar proportion inpercentage of structural units of the dihydroxy compound which arecontained in the resultant polycarbonate resin by the molar proportionin percentage of the dihydroxy compound which is being fed as a startingmaterial to the reactors is 0.03 or less in terms of absolute value withrespect to at least one dihydroxy compound and is not larger than 0.05in terms of absolute value with respect to each of all dihydroxycompounds.

[Chem. 23]

CH₂—O  (1)

(The case where the portion represented by general formula (1) is partof —CH₂—O—H is excluded.)

This process is explained in more detail. The reactors, heating means,reflux condenser, temperature conditions for each device, and the likeare as explained above with regard to the second production process. Inthe third production process, however, a plurality of dihydroxycompounds are used as a starting material. When the molar proportions inpercentage of the dihydroxy compounds fed as a starting material to thereactors are expressed respectively by A, B, C . . . N (% by mole) andthe molar proportions in percentage of structural units in the resultantpolycarbonate resin which are derived from the respective dihydroxycompounds are respectively expressed by a, b, c . . . n (% by mole),then at least one of (|(a−A)/A|, |(b−B)/B|, |(c−C)/C|, . . . ,|(n−N)/N|) is 0.03 or less, preferably 0.02 or less, more preferably0.01 or less, especially preferably 0.005 or less. Those absolute valuesfor the respective dihydroxy compounds each must be less than 0.05, andare preferably 0.03 or less, more preferably 0.02 or less, even morepreferably 0.01 or less, especially preferably 0.005 or less. Thesevalues can be attained by suitably selecting the kind and amount of acatalyst, transesterification reaction temperature (internaltemperature), temperature of the heating medium, pressure, residencetime, refluxing conditions, etc. as described above.

(Dihydroxy Compounds)

In the second and third processes of the invention, the dihydroxycompounds described above are suitable for the dihydroxy compounds to beused as starting-material monomers.

(Carbonic Diester)

In the second and third processes of the invention, the carbonicdiesters described above are suitable for the carbonic diester to beused as a starting-material monomer.

In the second and third processes of the invention, it is preferred thatthe dihydroxy compounds and carbonic diester as starting materialsshould be evenly mixed prior to the transesterification reaction.

The temperature at which the starting materials are mixed together isgenerally 80° C. or higher, preferably 90° C. or higher, and the upperlimit thereof is generally 250° C. or lower, preferably 200° C. orlower, more preferably 150° C. or lower. Especially suitable is atemperature of 100-120° C. In the case where the mixing temperature istoo low, there is the possibility of resulting in too low a dissolutionrate or in insufficient solubility. In addition, there are often thecases where troubles such as solidification arise. When the mixingtemperature is too high, there are the cases where the dihydroxycompounds deteriorate thermally. There is hence a possibility that thepolycarbonate resin obtained has an impaired hue and this adverselyaffects light resistance and heat resistance.

It is preferred in the second and third processes of the invention thatan operation for mixing the starting materials, i.e., dihydroxycompounds including the dihydroxy compound according to the inventionand a carbonic diester, should be conducted in an atmosphere having anoxygen concentration of generally 10 vol % or less. From the standpointof preventing hue deterioration, it is preferred to conduct theoperation in an atmosphere having an oxygen concentration of 0.0001-10vol %, in particular 0.0001-5 vol %, especially 0.0001-1 vol %.

In the invention, the carbonic diester is used in such an amount thatthe molar proportion thereof to all dihydroxy compounds to be subjectedto the reaction, which include the dihydroxy compound according to theinvention, is generally 0.90-1.20, preferably 0.95-1.10, more preferably0.97-1.03, especially preferably 0.99-1.02. Either too high or too lowmolar proportions thereof result in a decrease in the rate oftransesterification reaction and enhanced heat history during thepolymerization reaction.

There hence is a possibility that the resultant polycarbonate resinmight have an impaired hue. There also is a possibility that a desiredhigh-molecular polymer might not be obtained.

(Transesterification Catalyst)

In the second and third production processes of the invention, atransesterification catalyst is made to be present when dihydroxycompounds including the dihydroxy compound according to the inventionare condensation-polymerized with a carbonic diester by means of atransesterification reaction as described above. Namely, a specificcompound is made to be present in the first reactor from which themonohydroxy compound generated as a by-product of the polymerizationreaction is distilled off in an amount at least 20% of a theoreticaldistillation removal amount.

The transesterification reaction catalyst (polymerization catalyst) usedin the processes of the invention can affect light transmittance asmeasured especially at a wavelength of 350 nm and yellowness index (YI)value.

The transesterification catalysts described above are suitable for thetransesterification catalyst to be used.

The amount of the catalyst to be used is usually preferably 0.1-300μmol, more preferably 0.5-100 μmol, per mole of all dihydroxy compoundsused. Especially in the case where use is made of one or more compoundsof at least one metal selected from lithium and the Group-2 metals ofthe long-form periodic table, the amount of this catalyst is generally0.1 μmol or more, preferably 0.5 μmol or more, especially preferably 0.7μmol or more, in terms of metal amount per mole of all dihydroxycompounds used. The suitable upper limit thereof is generally 20 μmol,preferably 10 μmol, more preferably 3 μmol, especially preferably 1.5μmol, in particular 1.0 μmol.

The catalyst may be directly introduced into the reactor. Alternatively,use may be made of a method in which the catalyst is introduced into astarting-material preparation tank for mixing the dihydroxy compoundswith the carbonic diester beforehand and is thereafter caused to bepresent in the reactor.

In the case where the catalyst is used in too small an amount,sufficient polymerization activity is not obtained and thepolymerization reaction proceeds at a reduced rate, making it difficultto obtain a polycarbonate resin having a desired molecular weight. Inaddition, the amount of starting-material monomers which areincorporated into the polycarbonate resin decreases and the amount ofmonomers which are distilled off together with the by-productmonohydroxy compound increases, resulting in a possibility that thematerial unit might decrease and additional energy might be required forthe recovery of the monomers. Furthermore, in the case ofcopolymerization using a plurality of dihydroxy compounds, the increasein the amount of monomers which are distilled off may be causative of adifference between the proportions of the monomers used as startingmaterials and the ratio among the constituent units in the productpolycarbonate resin which are derived from the monomer units.

On the other hand, when the catalyst is used in too large an amount,those problems caused by the excessively large amount of monomersdistilled off tend to be mitigated. However, too large catalyst amountsresult in a possibility that the polycarbonate resin obtained might havedeteriorated properties concerning hue, light resistance, thermalstability, etc.

There is a possibility that when Group-1 metals, especially sodium,potassium, and cesium, in particular, lithium, sodium, potassium, andcesium, are contained in a polycarbonate resin in a large amount, thesemetals might adversely affect the hue. These metals do not come onlyfrom the catalyst used but may come from starting materials and thereactor. Consequently, the total amount of compounds of those metals inthe polycarbonate resin is generally 1 weight ppm or less, preferably0.8 weight ppm or less, more preferably 0.7 weight ppm or less, in termsof metal amount.

The content of metals in a polycarbonate resin can be determined byrecovering the metals contained in the polycarbonate resin by atechnique such as wet ashing and then determining the amount of themetals using a technique such as atomic emission, atomic absorption, orinductively coupled plasma (ICP) spectroscopy.

In the invention, by inhibiting the monomers from volatilizing offduring the polymerization reaction, the molar ratio between thedihydroxy compounds and the carbonic diester which are used as startingmaterials can be kept at around the theoretical value of 1.00.Consequently, a polycarbonate resin having a high molecular weight and asatisfactory hue is obtained without lowering the rate ofpolymerization.

(Polycarbonate Resins Obtained)

It is preferred that the polycarbonate resins obtained by the second andthird production processes of the invention should be polycarbonateresins which each give a molded object (thickness, 3 mm) that has alight transmittance, as measured at a wavelength of 350 nm, of 60% orhigher. The light transmittance thereof is more preferably 65% orhigher, especially preferably 70% or higher. When the lighttransmittance thereof at that wavelength is less than 60%, there are thecases where this polycarbonate resin shows enhanced absorption and hasimpaired light resistance.

It is also preferred that the polycarbonate resins obtained by thesecond and third production processes of the invention should bepolycarbonate resins which each give a molded object (flat plate havinga thickness of 3 mm) that has a light transmittance, as measured at awavelength of 320 nm, of 30% or higher. This light transmittance of themolded object is more preferably 40% or higher, especially preferably50% or higher. In the case where the light transmittance thereof at thatwavelength is lower than 30%, the polycarbonate resin tends to haveimpaired light resistance.

It is preferred that the polycarbonate resins obtained by the second andthird production processes of the invention should be polycarbonateresins which each give a molded object (thickness, 3 mm) that has ayellowness index (YI) value, as measured with respect to transmittedlight in accordance with ASTM D1925-70, of 12 or less after having beenirradiated with light for 100 hours using a metal halide lamp in anenvironment of 63° C. and a relative humidity of 50% at an irradiancefor the wavelength range of 300-400 nm of 1.5 kW/m². The yellownessindex value thereof is more preferably 10 or less, especially preferably8 or less.

Furthermore, the polycarbonate resins obtained by the second and thirdprocesses of the invention each preferably are a polycarbonate resinwhich, when molded into a flat plate having a thickness of 3 mm andexamined, without being subjected to the irradiation using a metalhalide lamp as described above or the like, has a yellowness index value(i.e., initial yellowness index value; referred to as initial YI value)as measured with respect to transmitted light of generally 10 or less.The initial YI value thereof is more preferably 7 or less, especiallypreferably 5 or less. The difference in yellowness index value betweenbefore and after the metal halide lamp irradiation is preferably 6 orless, more preferably 4 or less, especially preferably 3 or less, interms of absolute value.

In the case where the initial yellowness index (YI) value thereofexceeds 10, this resin tends to have impaired light resistance. In thecase where the absolute value of the difference in yellowness index (YI)value between before and after the metal halide lamp irradiation exceeds6, there is a possibility that the resin might take a color when exposedto sunlight, artificial lighting, or the like over a long period tobecome unusable in applications where transparency is especiallyrequired and in other applications.

Moreover, the polycarbonate resins obtained by the second and thirdprocesses of the invention each preferably are a polycarbonate resinwhich, when molded into a flat plate having a thickness of 3 mm andexamined, has an L* value, as provided for by International IlluminationCommission (CIE) and measured with respect to transmitted light, ofgenerally 96.3 or higher. The L* value thereof is more preferably 96.6or higher, especially preferably 96.8 or higher. In the case where theL* value thereof is less than 96.3, the resin tends to have impairedlight resistance.

Such a polycarbonate resin can be produced by a process which satisfiesthe features of the invention described above, while taking measuressuch as, for example, limiting the concentration of specific metalsduring the polymerization, suitably selecting the kind and amount of acatalyst, suitably selecting a polymerization temperature andpolymerization period, reducing the content of compounds causative ofcoloring, such as residual monomers, residual phenol, and residualdiphenyl carbonate, and reducing the amount of impurities which arecontained in the starting-material monomers and serve as coloringmatter. In particular, the kind and amount of a catalyst, polymerizationtemperature, and polymerization period are important.

The molecular weights of the polycarbonate resins obtained by theproduction processes of the invention described above can be expressedin terms of reduced viscosity. The reduced viscosities thereof aregenerally 0.30 dL/g or higher, preferably 0.35 dL/g or higher. The upperlimit of the reduced viscosities thereof is preferably 1.20 dL/g orless, more preferably 1.00 dL/g or less, even more preferably 0.80 dL/gor less.

In the case where the reduced viscosities of the polycarbonate resinsare too low, there is a possibility that these polycarbonate resinsmight give molded articles having low mechanical strength. In the casewhere the reduced viscosities thereof are too high, these polycarbonateresins tend to show poor flowability during molding, resulting indecreases in productivity and moldability.

Incidentally, the reduced viscosity of a polycarbonate is determined bypreparing a solution thereof having a polycarbonate concentrationprecisely adjusted to 0.6 g/dL using methylene chloride as a solvent andmeasuring the viscosity of the solution with a Ubbelohde viscometer at atemperature of 20.0±0.1° C.

In each of the polycarbonate resins obtained by the production processesof the invention, the lower limit of the concentration of the end grouprepresented by the following structural formula (3) is usuallypreferably 20 μeq/g, more preferably 40 μeq/g, especially preferably 50μeq/g. The upper limit thereof is usually preferably 160 μeq/g, morepreferably 140 μeq/g, especially preferably 100 μeq/g.

In the case where the concentration of the end group represented by thefollowing structural formula (3) is too high, there is a possibilitythat even when the polycarbonate resin has a satisfactory hueimmediately after polymerization or during molding, the high end groupconcentration might result in a hue deterioration through exposure toultraviolet rays. Conversely, in the case where the concentrationthereof is too low, there is a possibility that this polycarbonate resinmight have reduced thermal stability.

Examples of methods for regulating the concentration of the end grouprepresented by the following structural formula (3) include: to regulatethe molar proportions of the starting materials, i.e., at least onedihydroxy compound including the dihydroxy compound according to theinvention and a carbonic diester; and to control factors during thetransesterification reaction, such as polymerization pressure,polymerization temperature, and the temperature of the reflux condenser,according to the volatility of the monomers. According to the invention,since monomer volatilization can be inhibited, it is easy to regulatethe end group concentration on the basis of the molar proportions of thestarting materials.

The polycarbonate resins obtained by the production processes of theinvention through polycondensation as described above are usuallysolidified by cooling and pelletized with a rotary cutter or the like.

Methods for the pelletization are not limited. Examples thereof include:a method in which the polycarbonate resin is discharged in a moltenstate from the final polymerization reactor, cooled and solidified in astrand form, and pelletized; a method in which the resin is fed in amolten state from the final polymerization reactor to a single- ortwin-screw extruder, melt-extruded, subsequently cooled and solidified,and pelletized; and a method which includes discharging the resin in amolten state from the final polymerization reactor, cooling andsolidifying the resin in a strand form, temporarily pelletizing theresin, thereafter feeding the resin to a single- or twin-screw extruderagain, melt-extruding the resin, and then cooling, solidifying, andpelletizing the resin.

During such operations, residual monomers can be removed byvolatilization under vacuum within the extruder. It is also possible toadd generally known additives such as a heat stabilizer, neutralizingagent, ultraviolet absorber, release agent, colorant, antistatic agent,slip agent, lubricant, plasticizer, compatibilizing agent, and flameretardant and knead the mixture within the extruder.

The temperature to be used for melt kneading in the extruder depends onthe glass transition temperature and molecular weight of thepolycarbonate resin. However, the melt kneading temperature is generally150-300° C., preferably 200-270° C., more preferably 230-260° C. In thecase where the melt kneading temperature is lower than 150° C., thepolycarbonate resin has a high melt viscosity and imposes an increasedload on the extruder, resulting in a decrease in productivity. In thecase where the melt kneading temperature is higher than 300° C., thepolycarbonate thermally deteriorates considerably, resulting in adecrease in mechanical strength due to the decrease in molecular weightand further resulting in coloring and gas evolution.

In the polycarbonate resin production processes of the invention, it isdesirable to dispose a filter in order to prevent inclusion of foreignmatter. The position where a filter is disposed preferably is on thedownstream side of the extruder. The rejection size (opening size) ofthe filter is preferably 100 μm or smaller in terms of 99% removalfiltration accuracy. Especially when the resin is for use in filmapplications or the like for which inclusion of minute foreign particlesshould be avoided, the opening size of the filter is preferably 40 μm orsmaller, more preferably 10 μm or smaller.

From the standpoint of preventing inclusion of foreign matter fromoccurring after extrusion, it is desirable to extrude the polycarbonateresin in a clean room having a cleanliness preferably higher than class7 defined in JIS B 9920 (2002), more preferably higher than class 6.

Furthermore, for cooling and pelletizing the extruded polycarbonateresin, it is preferred to use a cooling method such as air cooling orwater cooling. It is desirable that air from which airborne foreignmatter has been removed beforehand with a high-efficiency particulateair filter or the like should be used for the air cooling to preventairborne foreign matter from adhering again. In the case of conductingwater cooling, it is desirable to use water from which metallicsubstances have been removed with an ion-exchange resin or the like andfrom which foreign matter has been removed with a filter. It ispreferred that the filter to be used should have an opening size of10-0.45 μm in terms of 99% removal filtration accuracy.

The polycarbonate resins obtained by the production processes of theinvention can be formed into molded objects by generally knowntechniques such as injection molding, extrusion molding, and compressionmolding.

Before the polycarbonate resins are molded by various moldingtechniques, additives such as a heat stabilizer, neutralizing agent,ultraviolet absorber, release agent, colorant, antistatic agent, slipagent, lubricant, plasticizer, compatibilizing agent, and flameretardant can be incorporated into the polycarbonate resins according toneed by means of a tumbling mixer, supermixer, floating mixer,twin-cylinder mixer, Nauta mixer, Banbury mixer, extruder, or the like.

The polycarbonate resins obtained by the production processes of theinvention each can be kneaded together with one or more polymersselected, for example, from synthetic resins such as aromaticpolycarbonates, aromatic polyesters, aliphatic polyesters, polyamides,polystyrene, polyolefins, acrylic resins, amorphous polyolefins, ABS,and AS, biodegradable resins such as poly(lactic acid) and poly(butylenesuccinate), and rubbers, and used as a polymer alloy.

According to the invention, polycarbonate resins having excellent lightresistance, transparency, hue, heat resistance, thermal stability, andmechanical strength can be provided, and polycarbonate resins whichstably show these performances can be efficiently produced whilereducing monomer loss.

EXAMPLES

The invention will be explained below in more detail by reference toExamples. However, the invention should not be construed as beinglimited by the following Examples unless the invention departs from thespirit thereof.

Examples 1 to 3

In the following, properties of polycarbonates were evaluated by thefollowing methods.

(1) Measurement of Oxygen Concentration

The concentration of oxygen in a polymerization reactor was measuredwith an oxygen analyzer (1000RS, manufactured by AMI Inc.).

(2) Measurement of Reduced Viscosity

A sample of a polycarbonate resin was dissolved using methylene chlorideas a solvent to prepare a polycarbonate solution having a concentrationof 0.6 g/dL. Using a Ubbelohde viscometer manufactured by Moritomo RikaKogyo, a measurement was made at a temperature of 20.0±0.1° C. Therelative viscosity ηrel was determined from the flow-down time of thesolvent t₀ and the flow-down time of the solution t using the followingequation.

ηrel=t/t ₀

The specific viscosity lisp was determined from the relative viscosityusing the following equation.

ηsp=(η−η₀)/η₀ =ηrel−1

The specific viscosity was divided by the concentration c (g/dL) todetermine the reduced viscosity ηsp/c. The larger the value thereof, thehigher the molecular weight.

(3) Determination of Proportion of Structural Units derived from eachDihydroxy Compound in Polycarbonate Resin and Determination ofConcentration of Terminal Phenyl Groups

The proportion of structural units derived from each dihydroxy compoundand contained in a polycarbonate resin was determined in the followingmanner. Thirty milligrams of the polycarbonate resin was weighed out anddissolved in about 0.7 mL of chloroform-d to obtain a solution, and thissolution was introduced into a tube for NMR spectroscopy which had aninner diameter of 5 mm. The solution was examined for ¹H NMR spectrum atordinary temperature using JNM-AL400 (resonance frequency, 400 MHz),manufactured by JEOL Ltd. The proportions of structural units derivedfrom respective dihydroxy compounds were determined from an intensityratio among signals attributable to the structural units derived fromthe respective dihydroxy compounds. With respect to the concentration ofterminal phenyl groups, the polycarbonate resin was examined for ¹H NMRspectrum in the same manner as described above using1,1,2,2-tetrabromoethane as an internal reference, and the concentrationwas determined from an intensity ratio between a signal attributable tothe internal reference and a signal attributable to terminal phenylgroups.

(4) Determination of Concentration of Metals in Polycarbonate Resin

About 0.5 g of polycarbonate resin pellets were precisely weighed outand put in a microwave decomposition vessel manufactured by PerkinElmer,Inc., and 2 mL of 97% sulfuric acid was added thereto. This vessel wasclosed and heated with a microwave at 230° C. for 10 minutes. After thevessel was cooled to room temperature, 1.5 mL of 68% nitric acid wasadded to the contents. This vessel was closed, heated with a microwaveat 150° C. for 10 minutes, and then cooled again to room temperature. Tothe contents was added 2.5 mL of 68% nitric acid. This vessel was closedagain and heated with a microwave at 230° C. for 10 minutes tocompletely decompose the contents. After the vessel was cooled to roomtemperature, the liquid thus obtained was diluted with pure water andexamined for metal concentration with an ICP-MS apparatus manufacturedby Thermo Quest Corp.

(5) Determination of Concentration of Phenol and Concentration of DPC inPolycarbonate Resin

A 1.25-g portion of a polycarbonate resin sample was dissolved in 7 mLof methylene chloride to obtain a solution. Acetone was added thereto insuch an amount as to result in a total volume of 25 mL, therebyconducting reprecipitation. Subsequently, the liquid thus treated wasfiltered through a 0.2-μm disk filter and subjected to quantitativeanalysis by liquid chromatography.

(6) Method for Evaluating Initial Hue of Polycarbonate Resin

Pellets of a polycarbonate resin were dried at 110° C. for 10 hours in anitrogen atmosphere. Subsequently, the dried polycarbonate resin pelletswere fed to an injection molding machine (Type J75EII, manufactured byThe Japan Steel Works, Ltd.), and an operation for forminginjection-molded pieces (60 mm (width)×60 mm (length)×3 mm (thickness))was repeated under the conditions of a resin temperature of 220° C. anda molding cycle of 23 seconds. The injection-molded pieces obtained bythe 10th shot to the 20th shot were examined for yellowness index(initial YI) value and L* value with respect to thickness-directiontransmitted light using a color tester (CM-3700d, manufactured by KonicaMinolta Inc.), and an average thereof was calculated. The smaller the YIvalue, the less the yellowness and the better the quality. The largerthe L* value, the higher the lightness.

(7) Method for Evaluating Hue of Polycarbonate Resin which Stagnated inHeated State

In the evaluation of the initial hue of a polycarbonate resin describedabove, the molding cycle in the molding for forming injection-moldedpieces with the injection molding machine was changed to 60 secondsafter the 19th shot and the molding operation was repeated under theseconditions from the 20th shot to the 30th shot. The injection-moldedarticles obtained by the 30th shot were examined for YI value withrespect to thickness-direction transmitted light using the color tester,and an average thereof was calculated.

(8) Measurement of Light Transmittance at Wavelengths of 350 nm and 320nm

Injection-molded pieces (60 mm (width)×60 mm (length)×3 mm (thickness);10th shot to 20th shot) obtained in (6) above were examined forthickness-direction light transmittance using a spectrophotometer forultraviolet and visible regions (U2900, manufactured by HitachiHigh-Technologies Corp.), and an average thereof was calculated toevaluate the light transmittance.

(9) Ratio of Number of Moles of H Bonded to Aromatic Rings (A) to Numberof Moles of all H (A+B) (where B is the Number of Moles of H Not Bondedto Aromatic Rings)

Chloroform-d which had been mixed beforehand with tetramethylsilane(TMS) as an internal reference was examined alone for spectrum todetermine a ratio of the signal of the TMS to the signal of residual Hcontained in the chloroform-d. Subsequently, 30 mg of a polycarbonateresin was weighed out and dissolved in about 0.7 mL of the chloroform-d.This solution was introduced into a tube for NMR spectroscopy which hadan inner diameter of 5 mm and examined for ¹H NMR spectrum at ordinarytemperature using JNM-AL400 (resonance frequency, 400 MHz), manufacturedby JEOL Ltd. The integral of the signal of residual H contained in thechloroform-d (the integral being determined from the integral of thesignal of the TMS and from the ratio of the TMS to residual H containedin the chloroform-d as determined above) was subtracted from theintegral of a signal which appeared at 6.5-8.0 ppm in the resultant NMRchart, and the value obtained is expressed by a. On the other hand, theintegral of a signal which appeared at 0.5-6.5 ppm is expressed by b.Then, a/(a+b)=A/(A+B) holds. Consequently, the left side was determined.

(10) Metal Halide Lamp Irradiation Test

Metaling Weather Meter M6T, manufactured by Suga Test Instruments Co.,Ltd., was used. A horizontal Metaling Lamp and quartz were attachedthereto as a light source and an inner filter, respectively, and a #500filter was attached as an outer filter to the periphery of the lamp. Theapparatus was set so as to result in an irradiance for wavelength range300-400 nm of 1.5 kW/m², and a square surface of a flat plate (60 mm(width)×60 mm (length) δ 3 mm (thickness)) obtained by the 20th shot in(6) above was irradiated with light for 100 hours under the conditionsof 63° C. and a relative humidity of 50%. After the irradiation, theflat plate was examined for YI value in the same manner as in (6) above.

The abbreviations for compounds used in the following Examples are asfollows.

ISB: isosorbide (trade name, POLYSORB; manufactured by Roquette Freres)CHDM: 1,4-cyclohexanedimethanol (SKY CHDM, manufactured by New JapanChemical Co., Ltd., for Examples 1 and 2; CHDM manufactured by EastmanLtd. for Example 3)DEG: diethylene glycol (manufactured by Mitsubishi Chemical Corp.)BPA: bisphenol A (manufactured by Mitsubishi Chemical Corp.)DPC: diphenyl carbonate (manufactured by Mitsubishi Chemical Corp.)

Example 1 Example 1-1

ISB, CHDM, DPC which had been purified by distillation to reduce thechloride ion concentration thereof to 10 ppb or less, and calciumacetate monohydrate were introduced in an ISB/CHDM/DPC/calcium acetatemonohydrate molar ratio of 0.70/0.30/1.00/1.3×10⁻⁶ into a polymerizationreactor equipped with a stirrer and a reflux condenser regulated to 100°C. Nitrogen displacement was sufficiently conducted (oxygenconcentration, 0.0005-0.001 vol %). Subsequently, the contents wereheated with a heat medium, and stirring was initiated at the time whenthe internal temperature reached 100° C. The contents were melted andhomogenized while regulating the internal temperature to 100° C.Thereafter, heating was initiated, and the internal temperature waselevated to 210° C. over 40 minutes. At the time when the internaltemperature reached 210° C., the polymerization reactor was regulated soas to maintain this temperature and pressure reduction was initiatedsimultaneously. The internal pressure was reduced to 13.3 kPa (absolutepressure; the same applies hereinafter) over 90 minutes from the timewhen 210° C. had been reached. The contents were held for further 60minutes while maintaining that pressure. The phenol vapor whichgenerated as a by-product with the progress of the polymerizationreaction was introduced into the reflux condenser, in which steamregulated so as to have a temperature of 100° C. as measured at theinlet of the reflux condenser was used as a coolant. The monomeringredients contained in a slight amount in the phenol vapor werereturned to the polymerization reactor, and the phenol vapor, whichremained uncondensed, was subsequently introduced into a condenseremploying 45° C. warm water as a coolant and recovered.

After the internal pressure was temporarily returned to atmosphericpressure, the contents, which had been thus oligomerized, weretransferred to another polymerization reactor equipped with a stirrerand a reflux condenser regulated in the same manner as described above.Heating and pressure reduction were initiated, and the internaltemperature was elevated to 220° C. and the pressure was reduced to 200Pa, over 60 minutes. Thereafter, the internal temperature was elevatedto 230° C. and the pressure was reduced to 133 Pa or below, over 20minutes. At the time when a given stirring power was reached, thepressure was returned to atmospheric pressure. The contents weredischarged in the form of a strand and pelletized with a rotary cutter.

Using a twin-screw extruder having two vent holes (LABOTEX30HSS-32)manufactured by The Japan Steel Works, Ltd., the pellets obtained wereextruded into a strand form while regulating the outlet resintemperature to 250° C. The extrudate was cooled and solidified withwater, and then pelletized with a rotary cutter. In this operation, thevent holes were connected to a vacuum pump, and the pressure as measuredat the vent holes was regulated to 500 Pa. The results of analysis ofthe polycarbonate resin obtained and the results of evaluation thereofconducted by the methods described above are shown in Table 1. Thepolycarbonate resin obtained had low yellowness, excellent lightness,and a satisfactory color tone. This resin further had satisfactory lightresistance.

Example 1-2

The same procedure as in Example 1-1 was conducted, except that themolar proportions of ISB and CHDM were changed. As in Example 1-1, apolycarbonate resin which had low yellowness, excellent lightness, and asatisfactory color tone and which further had satisfactory lightresistance was obtained.

Example 1-3

The same procedure as in Example 1-1 was conducted, except that ISB,CHDM, DPC, and calcium acetate monohydrate were introduced in anISB/CHDM/DPC/calcium acetate monohydrate molar ratio of0.70/0.30/1.00/2.5×10⁻⁶. As in Example 1-1, a polycarbonate resin whichhad low yellowness, excellent lightness, and a satisfactory color toneand which further had satisfactory light resistance was obtained.

Example 1-4

The same procedure as in Example 1-1 was conducted, except that ISB,CHDM, DPC, and calcium acetate monohydrate were introduced in anISB/CHDM/DPC/calcium acetate monohydrate molar ratio of0.70/0.30/1.00/0.9×10⁻⁶. A polycarbonate resin which had loweryellowness, higher lightness, and a better color tone than in Example1-1 was obtained. This resin further had satisfactory light resistance.

Example 1-5

The same procedure as in Example 1-3 was conducted, except thatmagnesium acetate tetrahydrate was used in place of the calcium acetatemonohydrate. As in Example 1-3, a polycarbonate resin which had lowyellowness, excellent lightness, and a satisfactory color tone and whichfurther had satisfactory light resistance was obtained.

Example 1-6

The same procedure as in Example 1-3 was conducted, except that bariumacetate was used in place of the calcium acetate monohydrate. As inExample 1-3, a polycarbonate resin which had low yellowness, excellentlightness, and a satisfactory color tone and which further hadsatisfactory light resistance was obtained.

Example 1-7

The same procedure as in Example 1-3 was conducted, except that lithiumacetate was used in place of the calcium acetate monohydrate. As inExample 1-3, a polycarbonate resin which had low yellowness, excellentlightness, and a satisfactory color tone and which further hadsatisfactory light resistance was obtained.

Example 1-8

The same procedure as in Example 1-3 was conducted, except that DEG wasused in place of the CHDM. As in Example 1-3, a polycarbonate resinwhich had low yellowness, excellent lightness, and a satisfactory colortone and which further had satisfactory light resistance was obtained.

Example 1-9

The same procedure as in Example 1-3 was conducted, except that theevacuation through the vent holes of the extruder was omitted. Thepolycarbonate resin obtained had a slightly lower ultraviolettransmittance than in Example 1-3.

Example 1-10

The same procedure as in Example 1-3 was conducted, except that cesiumcarbonate was used in place of the calcium acetate monohydrate and thatthe temperature in the final stage of the polymerization was changed to226° C. The polycarbonate resin obtained had slightly lower lightresistance than in Example 1-3.

Comparative Example 1-1

The same procedure as in Example 1-3 was conducted, except that cesiumcarbonate was used in place of the calcium acetate monohydrate. Thepolycarbonate resin obtained had a lower ultraviolet transmittance, ahigher YI value, and lower lightness and light resistance than inExample 1-3.

Comparative Example 1-2

The same procedure as in Example 1-3 was conducted, except that ISB,CHDM, BPA, DPC, and calcium acetate monohydrate were introduced in anISB/CHDM/BPA/DPC/calcium acetate monohydrate molar ratio of0.70/0.20/0.10/1.00/2.5×10⁻⁶. The polycarbonate resin obtained had alower ultraviolet transmittance, a higher YI value, and lower lightnessand light resistance than in Example 1-3.

Comparative Example 1-3

The same procedure as in Example 1-3 was conducted, except that thetemperature in the final stage of the polymerization was changed to 260°C. The polycarbonate resin obtained had a lower ultraviolettransmittance, a higher YI value, and lower lightness and lightresistance than in Example 1-3.

Comparative Example 1-4

The same procedure as in Example 1-3 was conducted, except that cesiumcarbonate was introduced in place of the calcium acetate monohydrate inthe amount shown in Table 1 and that the temperature in the final stageof the polymerization was changed to 250° C. The polycarbonate resinobtained had a lower ultraviolet transmittance, a higher YI value, andlower lightness and light resistance than in Example 1-3.

TABLE 1 Example 1-1 1-2 1-3 1-4 1-5 1-6 1-7 Amount of catalyst used Mgμmol per — — — — 2.5 — — (metal amount) Ca mol of 1.3 1.3 2.5 0.9 — — —Ba dihydroxy — — — — — 2.5 — Li compounds — — — — — — 2.5 Cs — — — — — —— Poly- Proportion of ISB mol % 69.9 50.0 70.0 70.0 69.9 70.0 69.9carbonate structural units CHDM 30.1 50.0 30.0 30.0 30.1 30.0 30.1 resinderived from each DEG 0.0 0.0 0.0 0.0 0.0 0.0 0.0 dihydroxy compound BPA0.0 0.0 0.0 0.0 0.0 0.0 0.0 Concentration of Na, K, and weight ppm 0.60.8 0.6 0.6 0.6 0.6 0.6 Cs (total) Concentration of Li weight ppm <0.05<0.05 <0.05 <0.05 <0.05 <0.05 0.13 Reduced viscosity dL/g 0.48 0.60 0.510.50 0.49 0.47 0.49 Phenol content weight ppm 204 221 216 200 220 205207 DPC content weight ppm 25 24 25 21 26 21 24 Concentration ofterminal μeq/g 81 80 60 54 106 88 60 phenyl groups A/(A + B) mol/mol0.007 0.006 0.005 0.005 0.009 0.008 0.005 Molded Light transmittance at350 nm % 78 67 75 80 74 70 70 article Light transmittance at 320 nm % 5846 54 60 50 46 50 L* value — 96.9 96.5 96.7 97.0 96.7 96.5 96.5 YI — 3.24.4 4.1 3.0 4.2 5.5 5.1 YI value after metal halide — 5.2 6.5 7.0 4.77.4 9.0 8.5 lamp irradiation Difference in YI value — 2.0 2.1 2.9 1.73.2 3.5 3.4 between before and after metal halide lamp irradiation YIvalue after high- — 3.8 4.9 4.6 3.4 4.8 6.4 5.6 temperature residencetest Example Comparative Example 1-8 1-9 1-10 1-1 1-2 1-3 1-4 Amount ofcatalyst used Mg μmol per — — — — — — — (metal amount) Ca mol of 2.5 2.5— — 2.5 2.5 — Ba dihydroxy — — — — — — — Li compounds — — — — — — — Cs —— 2.5 2.5 — — 1.0 Poly- Proportion of ISB mol % 70.0 70.1 70.5 71.1 70.070.0 70.3 carbonate structural units CHDM 30.0 29.9 29.5 28.9 20.0 30.029.7 resin derived from each DEG 30.0 0.0 0.0 0.0 0.0 0.0 0.0 dihydroxycompound BPA 0.0 0.0 0.0 0.0 10.0 0.0 0.0 Concentration of Na, K, andweight ppm 0.3 0.6 2.5 2.5 0.2 0.6 1.1 Cs (total) Concentration of Liweight ppm <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 Reduced viscositydL/g 0.62 0.48 0.48 0.48 0.45 0.53 0.51 Phenol content weight ppm 2102390 245 221 201 185 239 DPC content weight ppm 21 44 25 30 175 20 24Concentration of terminal μeq/g 50 66 85 118 100 69 50 phenyl groupsA/(A + B) mol/mol 0.005 0.008 0.008 0.011 0.131 0.006 0.005 Molded Lighttransmittance at 350 nm % 72 68 60 53 35 50 45 article Lighttransmittance at 320 nm % 51 37 33 22 0 16 12 L* value — 96.7 96.4 96.396.2 95.5 96.2 96.0 YI — 4.5 5.9 7.5 8.0 12.0 9.0 9.6 YI value aftermetal halide — 7.6 10.2 12.5 14.1 37.5 16.2 10.5 lamp irradiationDifference in YI value — 3.1 4.3 5.0 6.1 25.5 7.2 0.9 between before andafter metal halide lamp irradiation YI value after high- — 5.2 6.5 7.48.8 15.5 10.3 9.0 temperature residence test Note A: number of moles ofH bonded to aromatic rings of polycarbonate resin B: number of moles ofH bonded to parts other than aromatic rings in polycarbonate resin

Example 2 Example 2-1

ISB, CHDM, DPC which had been purified by distillation to reduce thechloride ion concentration thereof to 10 ppb or less, and calciumacetate monohydrate were introduced in an ISB/CHDM/DPC/calcium acetatemonohydrate molar ratio of 0.70/0.30/1.00/1.3×10⁻⁶ into a polymerizationreactor equipped with a stirrer and a reflux condenser regulated to 100°C. Nitrogen displacement was sufficiently conducted (oxygenconcentration, 0.0005-0.001 vol %). Subsequently, the contents wereheated with a heat medium, and stirring was initiated at the time whenthe internal temperature reached 100° C. The contents were melted andhomogenized while regulating the internal temperature to 100° C.Thereafter, heating was initiated, and the internal temperature waselevated to 210° C. over 40 minutes. At the time when the internaltemperature reached 210° C., the polymerization reactor was regulated soas to maintain this temperature and pressure reduction was initiatedsimultaneously. The internal pressure was reduced to 13.3 kPa (absolutepressure; the same applies hereinafter) over 90 minutes from the timewhen 210° C. had been reached. The contents were held for further 60minutes while maintaining that pressure. The phenol vapor whichgenerated as a by-product with the progress of the polymerizationreaction was introduced into the reflux condenser, in which steamregulated so as to have a temperature of 100° C. as measured at theinlet of the reflux condenser was used as a coolant. The monomeringredients contained in a slight amount in the phenol vapor werereturned to the polymerization reactor, and the phenol vapor, whichremained uncondensed, was subsequently introduced into a condenseremploying 45° C. warm water as a coolant and recovered.

After the internal pressure was temporarily returned to atmosphericpressure, the contents, which had been thus oligomerized, weretransferred to another polymerization reactor equipped with a stirrerand a reflux condenser regulated in the same manner as described above.Heating and pressure reduction were initiated, and the internaltemperature was elevated to 220° C. and the pressure was reduced to 200Pa, over 60 minutes. Thereafter, the internal temperature was elevatedto 228° C. and the pressure was reduced to 133 Pa or below, over 20minutes. At the time when a given stirring power was reached, thepressure was returned to atmospheric pressure. The contents weredischarged in the form of a strand and pelletized with a rotary cutter.

Using a twin-screw extruder having two vent holes (LABOTEX30HSS-32)manufactured by The Japan Steel Works, Ltd., the pellets obtained wereextruded into a strand form while regulating the outlet resintemperature to 250° C. The extrudate was cooled and solidified withwater, and then pelletized with a rotary cutter. In this operation, thevent holes were connected to a vacuum pump, and the pressure as measuredat the vent holes was regulated to 500 Pa. The results of analysis ofthe polycarbonate resin obtained and the results of evaluation thereofconducted by the methods described above are shown in Table 2. Thepolycarbonate resin obtained had low yellowness, excellent lightness,and a satisfactory color tone. This resin further had satisfactory lightresistance.

Example 2-2

The same procedure as in Example 2-1 was conducted, except that themolar proportions of ISB and CHDM were changed. As in Example 2-1, apolycarbonate resin which had low yellowness, excellent lightness, and asatisfactory color tone and which further had satisfactory lightresistance was obtained.

Example 2-3

The same procedure as in Example 2-1 was conducted, except that ISB,CHDM, DPC, and calcium acetate monohydrate were introduced in anISB/CHDM/DPC/calcium acetate monohydrate molar ratio of0.70/0.30/1.00/2.5×10⁻⁶. As in Example 2-1, a polycarbonate resin whichhad low yellowness, excellent lightness, and a satisfactory color toneand which further had satisfactory light resistance was obtained.

Example 2-4

The same procedure as in Example 2-1 was conducted, except that ISB,CHDM, DPC, and calcium acetate monohydrate were introduced in anISB/CHDM/DPC/calcium acetate monohydrate molar ratio of0.70/0.30/1.00/0.9×10⁻⁶. A polycarbonate resin which had loweryellowness, higher lightness, and a better color tone than in Example2-1 was obtained. This resin further had satisfactory light resistance.

Example 2-5

The same procedure as in Example 2-3 was conducted, except thatmagnesium acetate tetrahydrate was used in place of the calcium acetatemonohydrate. As in Example 2-3, a polycarbonate resin which had lowyellowness, excellent lightness, and a satisfactory color tone and whichfurther had satisfactory light resistance was obtained.

Example 2-6

The same procedure as in Example 2-3 was conducted, except that bariumacetate was used in place of the calcium acetate monohydrate. As inExample 2-3, a polycarbonate resin which had low yellowness, excellentlightness, and a satisfactory color tone and which further hadsatisfactory light resistance was obtained.

Example 2-7

The same procedure as in Example 2-3 was conducted, except that lithiumacetate was used in place of the calcium acetate monohydrate. As inExample 2-3, a polycarbonate resin which had low yellowness, excellentlightness, and a satisfactory color tone and which further hadsatisfactory light resistance was obtained.

Example 2-8

The same procedure as in Example 2-3 was conducted, except that DEG wasused in place of the CHDM. As in Example 2-3, a polycarbonate resinwhich had low yellowness, excellent lightness, and a satisfactory colortone and which further had satisfactory light resistance was obtained.

Example 2-9

The same procedure as in Example 2-3 was conducted, except that theevacuation through the vent holes of the extruder was omitted. Thepolycarbonate resin obtained had a slightly lower ultraviolettransmittance than in Example 2-3.

Example 2-10

The same procedure as in Example 2-3 was conducted, except that cesiumcarbonate was introduced in place of the calcium acetate monohydrate inthe amount shown in Table 2 and that the temperature in the final stageof the polymerization was changed to 250° C. The polycarbonate resinobtained had slightly lower light resistance than in Example 2-3.

Comparative Example 2-1

The same procedure as in Example 2-3 was conducted, except that cesiumcarbonate was used in place of the calcium acetate monohydrate and thatthe final temperature in the polymerization was changed to 230° C. Thepolycarbonate resin obtained had a lower ultraviolet transmittance, ahigher YI value, and lower lightness and light resistance than inExample 2-3.

Comparative Example 2-2

The same procedure as in Example 2-3 was conducted, except that ISB,CHDM, BPA, DPC, and calcium acetate monohydrate were introduced in anISB/CHDM/BPA/DPC/calcium acetate monohydrate molar ratio of0.70/0.20/0.10/1.00/2.5×10⁻⁶ and that the final temperature in thepolymerization was changed to 230° C. The polycarbonate resin obtainedhad a lower ultraviolet transmittance, a higher YI value, and lowerlightness and light resistance than in Example 2-3.

Comparative Example 2-3

The same procedure as in Example 2-3 was conducted, except that thetemperature in the final stage of the polymerization was changed to 260°C. The polycarbonate resin obtained had a lower ultraviolettransmittance, a higher YI value, and lower lightness and lightresistance than in Example 2-3.

Comparative Example 2-4

The same procedure as in Example 2-3 was conducted, except that cesiumcarbonate was used in place of the calcium acetate monohydrate and thatthe temperature in the final stage of the polymerization was changed to226° C. The polycarbonate resin obtained had lower light resistance thanin Example 2-3.

TABLE 2 Example 2-1 2-2 2-3 2-4 2-5 2-6 2-7 Amount of catalyst used Mgμmol per — — — — 2.5 — — (metal amount) Ca mol of 1.3 1.3 2.5 0.9 — — —Ba dihydroxy — — — — — 2.5 — Li compounds — — — — — — 2.5 Cs — — — — — —— Poly- Proportion of ISB mol % 69.9 50.0 70.0 70.0 69.9 70.0 69.9carbonate structural units CHDM 30.1 50.0 30.0 30.0 30.1 30.0 30.1 resinderived from each DEG 0.0 0.0 0.0 0.0 0.0 0 0.0 dihydroxy compound BPA0.0 0.0 0.0 0.0 0.0 0.0 0.0 Concentration of Na, K, and weight ppm 0.60.8 0.6 0.6 0.6 0.6 0.6 Cs (total) Concentration of Li weight ppm <0.05<0.05 <0.05 <0.05 <0.05 <0.05 0.13 Reduced viscosity dL/g 0.48 0.59 0.510.51 0.49 0.46 0.50 Phenol content weight ppm 222 220 230 200 223 221210 DPC content weight ppm 22 22 24 28 28 24 25 Concentration ofterminal μeq/g 75 76 57 60 111 90 58 phenyl groups A/(A + B) mol/mol0.007 0.006 0.005 0.005 0.010 0.008 0.005 Molded Light transmittance at350 nm % 80 70 77 82 75 73 75 article Light transmittance at 320 nm % 6049 57 63 52 50 57 L* value — 97.0 96.6 96.8 97.2 96.7 96.6 96.7 YI — 3.14.2 3.9 2.8 4.1 5.2 4.9 YI value after metal halide — 5.0 6.4 6.7 4.57.3 8.5 8.2 lamp irradiation Difference in YI value — 1.9 2.2 2.8 1.73.2 3.3 3.3 between before and after metal halide lamp irradiation YIvalue after high- — 3.8 4.7 4.5 3.3 4.5 6.4 5.5 temperature residencetest Example Comparative Example 2-8 2-9 2-10 2-1 2-2 2-3 2-4 Amount ofcatalyst used Mg μmol per — — — — — — — (metal amount) Ca mol of 2.5 2.5— — 2.5 2.5 — Ba dihydroxy — — — — — — — Li compounds — — — — — — — Cs —— 1.0 2.5 — — 2.5 Poly- Proportion of ISB mol % 70.0 71.1 70.3 71.1 70.070.0 70.5 carbonate structural units CHDM 0.0 28.9 29.7 28.9 20.0 30.029.5 resin derived from each DEG 30.0 0.0 0.0 0.0 0.0 0.0 0.0 dihydroxycompound BPA 0.0 0.0 0.0 0.0 10.0 0.0 0.0 Concentration of Na, K, andweight ppm 0.3 0.6 1.1 2.5 0.2 0.6 2.5 Cs (total) Concentration of Liweight ppm <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 <0.05 Reduced viscositydL/g 0.61 0.49 0.51 0.48 0.45 0.53 0.48 Phenol content weight ppm 2102910 238 221 201 185 245 DPC content weight ppm 23 43 24 30 175 20 25Concentration of terminal μeq/g 60 60 50 118 100 69 85 phenyl groupsA/(A + B) mol/mol 0.006 0.008 0.005 0.011 0.090 0.006 0.008 Molded Lighttransmittance at 350 nm % 77 69 45 53 40 50 60 article Lighttransmittance at 320 nm % 58 40 12 22 0 16 33 L* value — 96.9 96.5 96.096.2 95.8 96.2 96.3 YI — 4.1 5.7 9.6 8.0 11.0 9.0 7.5 YI value aftermetal halide — 7.3 10.4 10.5 14.1 33.5 16.2 12.5 lamp irradiationDifference in YI value — 3.2 4.7 0.9 5.1 22.5 7.2 5.0 between before andafter metal halide lamp irradiation YI value after high- — 5.0 6.7 9.08.8 15.0 10.3 7.4 temperature residence test Note A: number of moles ofH bonded to aromatic rings of polycarbonate resin B: number of moles ofH bonded to parts other than aromatic rings in polycarbonate resin

Example 3 Example 3-1

ISB, CHDM, DPC which had been purified by distillation to reduce thechloride ion concentration thereof to 10 ppb or less, and calciumacetate monohydrate were introduced in an ISB/CHDM/DPC/calcium acetatemonohydrate molar ratio of 0.70/0.30/1.00/1.3×10⁻⁶ into a polymerizationreactor equipped with a stirrer and a reflux condenser regulated to 100°C. Nitrogen displacement was sufficiently conducted (oxygenconcentration, 0.0005-0.001 vol %). Subsequently, the contents wereheated with a heat medium, and stirring was initiated at the time whenthe internal temperature reached 100° C. The contents were melted andhomogenized while regulating the internal temperature to 100° C.Thereafter, heating was initiated, and the internal temperature waselevated to 215° C. over 40 minutes. At the time when the internaltemperature reached 215° C., the polymerization reactor was regulated soas to maintain this temperature and pressure reduction was initiatedsimultaneously. The internal pressure was reduced to 13.3 kPa (absolutepressure; the same applies hereinafter) over 90 minutes from the timewhen 215° C. had been reached. The contents were held for further 60minutes while maintaining that pressure. The phenol vapor whichgenerated as a by-product with the progress of the polymerizationreaction was introduced into the reflux condenser, in which steamregulated so as to have a temperature of 100° C. as measured at theinlet of the reflux condenser was used as a coolant. The monomeringredients contained in a slight amount in the phenol vapor werereturned to the polymerization reactor, and the phenol vapor, whichremained uncondensed, was subsequently introduced into a condenseremploying 45° C. warm water as a coolant and recovered.

After the internal pressure was temporarily returned to atmosphericpressure, the contents, which had been thus oligomerized, weretransferred to another polymerization reactor equipped with a stirrerand a reflux condenser regulated in the same manner as described above.Heating and pressure reduction were initiated, and the internaltemperature was elevated to 220° C. and the pressure was reduced to 200Pa, over 60 minutes. Thereafter, the internal temperature was elevatedto 230° C. and the pressure was reduced to 133 Pa or below, over 20minutes. At the time when a given stirring power was reached, thepressure was returned to atmospheric pressure. The contents weredischarged in the form of a strand and pelletized with a rotary cutter.

Using a twin-screw extruder having two vent holes (LABOTEX30HSS-32)manufactured by The Japan Steel Works, Ltd., the pellets obtained wereextruded into a strand form while regulating the outlet resintemperature to 250° C. The extrudate was cooled and solidified withwater, and then pelletized with a rotary cutter. In this operation, thevent holes were connected to a vacuum pump, and the pressure as measuredat the vent holes was regulated to 500 Pa. The results of analysis ofthe polycarbonate resin obtained and the results of evaluation thereofconducted by the methods described above are shown in Table 3. Thepolycarbonate resin obtained had low yellowness, excellent lightness,and a satisfactory color tone. This resin further had satisfactory lightresistance.

Example 3-2

The same procedure as in Example 3-1 was conducted, except that themolar proportions of ISB and CHDM were changed. As in Example 3-1, apolycarbonate resin which had low yellowness, excellent lightness, and asatisfactory color tone and which further had satisfactory lightresistance was obtained.

Example 3-3

The same procedure as in Example 3-1 was conducted, except that ISB,CHDM, DPC, and calcium acetate monohydrate were introduced in anISB/CHDM/DPC/calcium acetate monohydrate molar ratio of0.70/0.30/1.00/2.5×10⁻⁶. As in Example 3-1, a polycarbonate resin whichhad low yellowness, excellent lightness, and a satisfactory color toneand which further had satisfactory light resistance was obtained.

Example 3-4

The same procedure as in Example 3-1 was conducted, except that ISB,CHDM, DPC, and calcium acetate monohydrate were introduced in anISB/CHDM/DPC/calcium acetate monohydrate molar ratio of0.70/0.30/1.00/0.9×10⁻⁶. A polycarbonate resin which had loweryellowness, higher lightness, and a better color tone than in Example3-1 was obtained. This resin further had satisfactory light resistance.

Example 3-5

The same procedure as in Example 3-3 was conducted, except thatmagnesium acetate tetrahydrate was used in place of the calcium acetatemonohydrate. As in Example 3-3, a polycarbonate resin which had lowyellowness, excellent lightness, and a satisfactory color tone and whichfurther had satisfactory light resistance was obtained.

Example 3-6

The same procedure as in Example 3-3 was conducted, except that bariumacetate was used in place of the calcium acetate monohydrate. As inExample 3-3, a polycarbonate resin which had low yellowness, excellentlightness, and a satisfactory color tone and which further hadsatisfactory light resistance was obtained.

Example 3-7

The same procedure as in Example 3-3 was conducted, except that lithiumacetate was used in place of the calcium acetate monohydrate. As inExample 3-3, a polycarbonate resin which had low yellowness, excellentlightness, and a satisfactory color tone and which further hadsatisfactory light resistance was obtained.

Example 3-8

The same procedure as in Example 3-3 was conducted, except that DEG wasused in place of the CHDM. As in Example 3-3, a polycarbonate resinwhich had low yellowness, excellent lightness, and a satisfactory colortone and which further had satisfactory light resistance was obtained.

Example 3-9

The procedure in Example 3-1 was conducted in which the set value offinal stirring power for polymerization was lowered. Thus, polycarbonateresin pellets having a reduced viscosity of 0.40 dL/g and a phenolcontent of 3,500 weight ppm were obtained. In a nitrogen atmosphere, thepolycarbonate resin pellets were melted with a single-screw extruderhaving a barrel temperature set at 230° C., and the melt was introducedinto a horizontal reactor having two stirring shafts extendinghorizontally and a plurality of stirring blades discontinuously disposedon each shaft (manufactured by Hitachi Plant Technologies, Ltd.;spectacle-shaped blades; effective capacity, 6 L). The horizontalreactor was regulated so as to have an internal pressure of 133 Pa andan internal temperature of 230° C., and a polycondensation reaction wascontinuously performed for 60 minutes. The molten polycarbonate resinwas discharged in the form of a strand and pelletized with a rotarycutter. The polycarbonate resin obtained had a reduced viscosity of 0.50dL/g and a phenol concentration of 204 weight ppm.

Comparative Example 3-1

The same procedure as in Example 3-1 was conducted, except that cesiumcarbonate was used in place of the calcium acetate monohydrate. Theresultant polycarbonate resin tended to have a lower ultraviolettransmittance and a higher initial YI value than in Example 3-1. Thisresin further had lower lightness and light resistance.

Comparative Example 3-2

The same procedure as in Comparative Example 3-1 was conducted, exceptthat the evacuation through the vent holes of the extruder was omitted.The polycarbonate resin obtained had a lower ultraviolet transmittance,a higher initial YI value, and lower lightness and light resistance thanin Comparative Example 3-1.

Comparative Example 3-3

The same procedure as in Example 3-1 was conducted, except that theamount of the calcium acetate monohydrate was increased as shown inTable 3. The polycarbonate resin obtained had a lower ultraviolettransmittance, a higher initial YI value, and lower lightness and lightresistance than in Example 3-1.

Comparative Example 3-4

The same procedure as in Example 3-3 was conducted, except that thetemperature in the final stage of the polymerization was changed to 260°C. and that the evacuation through the vent holes of the extruder wasomitted. The polycarbonate resin obtained had a lower ultraviolettransmittance, a higher initial YI value, and lower lightness and lightresistance than in Example 3-3.

TABLE 3 Example 3-1 3-2 3-3 3-4 3-5 3-6 3-7 Amount of catalyst used Mgμmol per — — — — 2.5 — — (metal amount) Ca mol of 1.3 1.3 2.5 0.9 — — —Ba dihydroxy — — — — — 2.5 — Li compounds — — — — — — 2.5 Cs — — — — — —— Poly- Proportion of ISB mol % 69.9 50.0 70.0 70.2 70.0 70.0 70.0carbonate structural units CHDM 30.1 50.0 30.0 29.8 30.0 30.0 30.0 resinderived from each DEG 0.0 0.0 0.0 0.0 0.0 0.0 0.0 dihydroxy compound BPA0.0 0.0 0.0 0.0 0.0 0.0 0.0 Concentration of Na, K, and weight ppm 0.60.8 0.6 0.6 0.6 0.6 0.6 Cs (total) Concentration of Li weight ppm <0.05<0.05 <0.05 <0.05 <0.05 <0.05 0.13 Reduced viscosity dL/g 0.48 0.60 0.500.51 0.48 0.48 0.50 Phenol content weight ppm 205 230 220 222 232 230205 DPC content weight ppm 26 25 25 24 28 21 26 Concentration ofterminal μeq/g 75 77 58 50 100 84 52 phenyl groups A/(A + B) mol/mol0.007 0.006 0.005 0.005 0.009 0.008 0.005 Molded Light transmittance at350 nm % 77 67 73 80 72 69 70 article Light transmittance at 320 nm % 5745 51 59 50 46 50 L* value — 96.9 96.4 96.6 97.0 96.7 96.5 96.5 InitialYI value — 3.3 4.6 4.3 3.1 4.4 5.7 5.2 YI value after metal halide — 5.46.7 7.1 4.7 7.5 9.0 8.5 lamp irradiation Difference in YI value — 2.12.1 2.8 1.6 3.1 3.3 3.3 between before and after metal halide lampirradiation YI value after high- — 3.9 4.9 4.6 3.5 4.8 6.4 5.8temperature residence test Example Comparative Example 3-8 3-9 3-1 3-23-3 3-4 Amount of catalyst used Mg μmol per — — — — — — (metal amount)Ca mol of 2.5 1.3 — — 25.0 2.5 Ba dihydroxy — — — — — — Li compounds — —— — — — Cs — — 1.3 1.3 — — Poly- Proportion of ISB mol % 70.0 70.0 71.171.1 70.0 70.0 carbonate structural units CHDM 0.0 30.0 28.9 28.9 30.030.0 resin derived from each DEG 30.0 0.0 0.0 0.0 0.0 0.0 dihydroxycompound BPA 0.0 0.0 0.0 0.0 0.0 0.0 Concentration of Na, K, and weightppm 0.3 0.6 1.5 1.5 0.6 0.6 Cs (total) Concentration of Li weight ppm<0.05 <0.05 <0.05 <0.05 <0.05 <0.05 Reduced viscosity dL/g 0.63 0.500.50 0.50 0.51 0.53 Phenol content weight ppm 210 204 209 2220 250 2550DPC content weight ppm 20 8 24 45 25 45 Concentration of terminal μeq/g50 50 90 95 110 60 phenyl groups A/(A + B) mol/mol 0.005 0.005 0.0080.010 0.010 0.008 Molded Light transmittance at 350 nm % 71 81 60 50 4447 article Light transmittance at 320 nm % 50 60 30 24 0 13 L* value —96.6 97.0 96.4 96.0 95.0 95.9 Initial YI value — 4.7 2.9 7.0 8.0 12.510.7 YI value after metal halide — 7.8 4.4 12.0 13.5 20.9 18.3 lampirradiation Difference in YI value — 3.1 1.5 5.0 5.5 8.4 7.6 betweenbefore and after metal halide lamp irradiation YI value after high- —5.3 3.4 8.0 9.2 15.1 14.5 temperature residence test

Example 4

In the following, properties of polycarbonates were evaluated by thefollowing methods.

(1) Measurement of Oxygen Concentration

The concentration of oxygen in a polymerization reactor was measuredwith an oxygen analyzer (1000RS, manufactured by AMI Inc.).

(2) Determination of Amounts of Monomers and Phenol Distilled Off

The weights of the monomers and phenol which were distilled off in eachreaction stage were determined from a composition determined by liquidchromatography.

(3) Calculation of Proportion (% by Weight) of Total Amount of MonomersDistilled Off to Sum of Starting-Material Monomers

The proportion of the total amount of all monomers distilled off to thesum of starting-material monomers was calculated from the total amountof all the monomers distilled off including diphenyl carbonate which wasdetermined in (2) above and from the sum of all the monomers fed as thestarting-materials.

(4) Measurement of Reduced Viscosity

A sample of a polycarbonate resin was dissolved using methylene chlorideas a solvent to prepare a polycarbonate solution having a concentrationof 0.6 g/dL. Using a Ubbelohde viscometer manufactured by Moritomo RikaKogyo, a measurement was made at a temperature of 20.0±0.1° C. Therelative viscosity ηrel was determined from the flow-down time of thesolvent t₀ and the flow-down time of the solution t using the followingequation.

ηrel=t/t ₀

The specific viscosity ηsp was determined from the relative viscosityusing the following equation.

ηsp=(η−η₀)/η₀ =ηrel−1

The specific viscosity was divided by the concentration c (g/dL) todetermine the reduced viscosity ηsp/c. The larger the value thereof, thehigher the molecular weight.

(5) Determination of Proportion of Structural Units Derived from EachDihydroxy Compound in Polycarbonate Resin and Determination ofConcentration of Terminal Phenyl Groups

The proportion of structural units of each dihydroxy compound which werecontained in a polycarbonate resin was determined in the followingmanner. Thirty milligrams of the polycarbonate resin was weighed out anddissolved in about 0.7 mL of chloroform-d to obtain a solution, and thissolution was introduced into a tube for NMR spectroscopy which had aninner diameter of 5 mm. The solution was examined for ¹H NMR spectrum atordinary temperature using JNM-AL400 (resonance frequency, 400 MHz),manufactured by JEOL Ltd. The proportions of structural units derivedfrom respective dihydroxy compounds were determined from an intensityratio among signals attributable to the structural units derived fromthe respective dihydroxy compounds.

With respect to the concentration of terminal phenyl groups, thepolycarbonate resin was examined for ¹H NMR spectrum in the same manneras described above using 1,1,2,2-tetrabromoethane as an internalreference, and the concentration was determined from an intensity ratiobetween a signal attributable to the internal reference and a signalattributable to terminal phenyl groups.

(6) Difference Between Proportion of Each Dihydroxy Compound Fed asStarting Material and Proportion of Structural Units Derived from theDihydroxy Compound in Polycarbonate Resin Obtained

The title difference was evaluated from the absolute value of the resultobtained by dividing the difference between the molar proportion inpercentage of structural units of each dihydroxy compound in thepolycarbonate resin which was determined in (5) above and the molarproportion in percentage of the dihydroxy compound fed as a startingmaterial, by the molar proportion in percentage of the dihydroxycompound fed as a starting material. The lager the absolute value, thelarger the title difference.

(7) Determination of Concentration of Metals in Polycarbonate Resin

About 0.5 g of polycarbonate resin pellets were precisely weighed outand put in a microwave decomposition vessel manufactured by PerkinElmer,Inc., and 2 mL of 97% sulfuric acid was added thereto. This vessel wasclosed and heated with a microwave at 230° C. for 10 minutes. After thevessel was cooled to room temperature, 1.5 mL of 68% nitric acid wasadded to the contents. This vessel was closed, heated with a microwaveat 150° C. for 10 minutes, and then cooled again to room temperature. Tothe contents was added 2.5 mL of 68% nitric acid. This vessel was closedagain and heated with a microwave at 230° C. for 10 minutes tocompletely decompose the contents. After the vessel was cooled to roomtemperature, the liquid thus obtained was diluted with pure water andthe concentration of metals therein was determined with an ICP-MSapparatus manufactured by ThermoQuest Corp.

(8) Method for Evaluating Initial Hue of Polycarbonate Resin

Pellets of a polycarbonate resin were dried at 110° C. for 10 hours in anitrogen atmosphere. Subsequently, the dried polycarbonate resin pelletswere fed to an injection molding machine (Type J75EII, manufactured byThe Japan Steel Works, Ltd.), and an operation for forminginjection-molded pieces (60 mm (width)×60 mm (length)×3 mm (thickness))was repeated under the conditions of a resin temperature of 220° C. anda molding cycle of 23 seconds. The injection-molded pieces obtained bythe 10th shot to the 20th shot were examined for yellowness index (YI)value and L* value with respect to thickness-direction transmitted lightusing a color tester (CM-3700d, manufactured by Konica Minolta Inc.),and an average thereof was calculated. The smaller the YI value, theless the yellowness and the better the quality. The larger the L* value,the higher the lightness.

(9) Light Transmittance at Wavelengths of 350 nm and 320 nm

Injection-molded pieces (60 mm (width)×60 mm (length)×3 mm (thickness);10th shot to 20th shot) obtained in (8) above were examined forthickness-direction light transmittance using a spectrophotometer forultraviolet and visible regions (U2900, manufactured by HitachiHigh-Technologies Corp.), and an average thereof was calculated toevaluate the light transmittance.

(10) Metal Halide Lamp Irradiation Test

Metaling Weather Meter M6T, manufactured by Suga Test Instruments Co.,Ltd., was used. A horizontal Metaling Lamp and quartz were attachedthereto as a light source and an inner filter, respectively, and a #500filter was attached as an outer filter to the periphery of the lamp. Theapparatus was set so as to result in an irradiance for wavelength range300-400 nm of 1.5 kW/m², and a square surface of a flat plate (60 mm(width)×60 mm (length)×3 mm (thickness)) obtained by the 20th shot in(8) above was irradiated with light for 100 hours under the conditionsof 63° C. and a relative humidity of 50%. After the irradiation, theflat plate was examined for YI value in the same manner as in (8) above.

The abbreviations for compounds used in the following Examples are asfollows.

ISB: isosorbide (trade name, POLYSORB; manufactured by Roquette Freres)CHDM: 1,4-cyclohexanedimethanol (trade name, SKY CHDM; manufactured byNew Japan Chemical Co., Ltd.)DEG: diethylene glycol (manufactured by Mitsubishi Chemical Corp.)DPC: diphenyl carbonate (manufactured by Mitsubishi Chemical Corp.)

Example 4-1 First-Stage Reaction

Into a 40-L polymerization reactor equipped with a heating medium jacketemploying an oil as a heating medium, a stirrer, and a distillate tubeconnected to a vacuum pump were introduced 30.44 mol of ISB, 13.04 molof CHDM, and 43.48 mol of DPC which had been purified by distillation toreduce the chloride ion concentration thereof to 10 ppb or less. Calciumacetate monohydrate in the form of an aqueous solution was introduced inan amount of 1.25×10⁻⁶ mol per mole of all dihydroxy compounds.Thereafter, nitrogen displacement was sufficiently conducted (oxygenconcentration, 0.0005-0.001 vol %). The distillate tube was providedwith a reflux condenser employing steam (inlet temperature, 100° C.) asa coolant and with a condenser which employed warm water (inlettemperature, 45° C.) as a coolant and was disposed downstream from thereflux condenser. Subsequently, the heated heating medium was passedthrough the reactor and, at the time when the temperature of the liquidreaction mixture (i.e., internal temperature) reached 100° C., stirringwas initiated.

The contents were melted and homogenized while keeping the internaltemperature at 100° C. Thereafter, heating was initiated, and theinternal temperature was elevated to 220° C. over 40 minutes. At thetime when the internal temperature reached 220° C., pressure reductionwas initiated and the system was regulated so that the internal pressuredecreased to 13.3 kPa (absolute pressure, the same applies hereinafter)over 90 minutes. Upon the initiation of pressure reduction, the vapor ofphenol which had been generated by the reaction rapidly began to bedistilled off. The temperature of the oil being introduced into theheating medium jacket (heating medium jacket inlet temperature) wassuitably regulated so that the internal temperature was kept constant at220° C. The temperature of the heating-medium oil was regulated to 242°C. during the period when phenol was distilled off in an increasedamount, and was regulated so as to be lower than 242° C. during theother periods.

After the internal pressure was reduced to 13.3 kPa, the contents wereheld for further 60 minutes while maintaining that pressure. Thus, apolycarbonate oligomer was obtained.

The phenol which generated as a by-product of the polymerizationreaction and the monomers which were distilled off were partly condensedby means of the reflux condenser and returned to the polymerizationreactor. The phenol, which remained uncondensed, and the monomers whichhad not been condensed in the reflux condenser were introduced into thecondenser and recovered. The phenol which was distilled off in thisstage amounted to 94% of a theoretical distillation removal amount.

(Second-Stage Reaction)

In a nitrogen atmosphere, the polycarbonate oligomer obtained in thefirst stage was transferred to a polymerization reactor equipped with aheating medium jacket employing an oil as a heating medium, a stirrer,and a distillate tube connected to a vacuum pump. The distillate tubewas provided with a reflux condenser employing steam (inlet temperature,100° C.) as a coolant and with a condenser which employed warm water(inlet temperature, 45° C.) as a coolant and was disposed downstreamfrom the reflux condenser. The distillate tube was further provided,downstream from the condenser, with a cold trap employing dry ice as acoolant.

After the transfer of the oligomer, pressure reduction was initiated,and the internal temperature was elevated to 220° C. and the pressurewas reduced to 200 Pa, over 60 minutes. Thereafter, the internaltemperature was elevated to 230° C. and the pressure was reduced to 133Pa or below, over 20 minutes. At the time when a given stirring powerwas reached, the pressure was returned to atmospheric pressure. Thecontents were discharged in the form of a strand and pelletized with arotary cutter. In this operation, the period from the time when thepressure became 1 kPa to the time when the given stirring power wasreached was measured.

The phenol which generated as a by-product of the polymerizationreaction and the monomers which were distilled off were partly condensedby means of the reflux condenser and returned to the polymerizationreactor. The phenol, which remained uncondensed, and the monomers whichhad not been condensed in the reflux condenser were introduced into thecondenser and recovered. Furthermore, the fraction which had not beencondensed in the condenser was recovered with the cold trap disposeddownstream from the condenser.

The fractions recovered through the reflux condenser, condenser, andcold trap in each reaction stage were weighed and examined forcomposition to determine the amounts of the by-product phenol andmonomers which had been distilled off. The thus-determined weights ofthe monomers distilled off in the respective stages were summed up, andthe ratio of the total to the amount of the monomers fed as startingmaterials was calculated and shown in Table 4.

Using a twin-screw extruder having two vent holes (LABOTEX30HSS-32)manufactured by The Japan Steel Works, Ltd., the pellets obtained wereextruded into a strand form while regulating the outlet resintemperature to 250° C. The extrudate was cooled and solidified withwater, and then pelletized with a rotary cutter. In this operation, thevent holes were connected to a vacuum pump, and the pressure as measuredat the vent holes was regulated to 500 Pa.

The results of analysis of the polycarbonate resin obtained and theresults of evaluation thereof conducted by the methods described aboveare shown in Table 4. The amount of the monomers distilled off wassmall, and the difference between the proportion of each dihydroxycompound fed as a starting material and the proportion of structuralunits of the dihydroxy compound in the polycarbonate resin obtained wassmall. A polycarbonate resin having low yellowness, excellent lightness,and a satisfactory color tone was obtained. The resin further hadsatisfactory light resistance.

Example 4-2

The same procedure as in Example 4-1 was conducted, except that themolar proportions of ISB and CHDM were changed and that the maximumtemperature of the heat medium in the first-stage reaction was changed.As in Example 4-1, the amount of the monomers distilled off was small,and the difference between the proportion of each dihydroxy compound fedas a starting material and the proportion of structural units of thedihydroxy compound in the polycarbonate resin obtained was small. Apolycarbonate resin which had low yellowness, excellent lightness, and asatisfactory color tone and which further had satisfactory lightresistance was obtained as in Example 4-1.

Example 4-3

The same procedure as in Example 4-1 was conducted, except that calciumacetate monohydrate was introduced in an amount of 2.50×10⁻⁶ mol permole of all dihydroxy compounds and that the maximum temperature of theheat medium in the first-stage reaction was changed to 244° C. As inExample 4-1, the amount of the monomers distilled off was small, and thedifference between the proportion of each dihydroxy compound fed as astarting material and the proportion of structural units of thedihydroxy compound in the polycarbonate resin obtained was small. Apolycarbonate resin which had low yellowness, excellent lightness, and asatisfactory color tone and which further had satisfactory lightresistance was obtained as in Example 4-1.

Example 4-4

The same procedure as in Example 4-1 was conducted, except that calciumacetate monohydrate was introduced in an amount of 0.90×10⁻⁶ mol permole of all dihydroxy compounds and that the maximum temperature of theheat medium in the first-stage reaction was changed to 239° C. As inExample 4-1, the amount of the monomers distilled off was small, and apolycarbonate resin was obtained in which the difference between theproportion of each dihydroxy compound fed as a starting material and theproportion of structural units of the dihydroxy compound in thepolycarbonate resin obtained was small. This polycarbonate resin hadlower yellowness, better lightness, and better light resistance than inExample 4-1.

Example 4-5

The same procedure as in Example 4-1 was conducted, except that calciumacetate monohydrate was introduced in an amount of 0.25×10⁻⁶ mol permole of all dihydroxy compounds and that the maximum temperature of theheat medium in the first-stage reaction was changed to 233° C. The rateof polymerization in the second stage was lower and the amount of themonomers distilled off was slightly larger, as compared with those inExample 4-1. However, a polycarbonate resin having low yellowness,excellent lightness, and a satisfactory color tone was obtained. Thisresin further had satisfactory light resistance.

Example 4-6

The same procedure as in Example 4-3 was conducted, except thatmagnesium acetate tetrahydrate was used in place of the calcium acetatemonohydrate and that the maximum temperature of the heat medium in thefirst-stage reaction was changed. As in Example 4-3, the amount of themonomers distilled off was small, and the difference between theproportion of each dihydroxy compound fed as a starting material and theproportion of structural units of the dihydroxy compound in thepolycarbonate resin obtained was small. A polycarbonate resin which hadlow yellowness, excellent lightness, and a satisfactory color tone andwhich further had satisfactory light resistance was obtained as inExample 4-3.

Example 4-7

The same procedure as in Example 4-3 was conducted, except that bariumacetate was used in place of the calcium acetate monohydrate and thatthe maximum temperature of the heat medium in the first-stage reactionwas changed. As in Example 4-3, the amount of the monomers distilled offwas small, and the difference between the proportion of each dihydroxycompound fed as a starting material and the proportion of structuralunits of the dihydroxy compound in the polycarbonate resin obtained wassmall. A polycarbonate resin which had low yellowness, excellentlightness, and a satisfactory color tone and which further hadsatisfactory light resistance was obtained as in Example 4-3.

Example 4-8

The same procedure as in Example 4-3 was conducted, except that lithiumacetate was used in place of the calcium acetate monohydrate and thatthe maximum temperature of the heat medium in the first-stage reactionwas changed. As in Example 4-3, the amount of the monomers distilled offwas small, and the difference between the proportion of each dihydroxycompound fed as a starting material and the proportion of structuralunits of the dihydroxy compound in the polycarbonate resin obtained wassmall. A polycarbonate resin which had low yellowness, excellentlightness, and a satisfactory color tone and which further hadsatisfactory light resistance was obtained as in Example 4-3.

Example 4-9

The same procedure as in Example 4-3 was conducted, except that DEG wasused in place of the CHDM and that the maximum temperature of the heatmedium in the first-stage reaction was changed. As in Example 4-3, theamount of the monomers distilled off was small, and the differencebetween the proportion of each dihydroxy compound fed as a startingmaterial and the proportion of structural units of the dihydroxycompound in the polycarbonate resin obtained was small. A polycarbonateresin which had low yellowness, excellent lightness, and a satisfactorycolor tone and which further had satisfactory light resistance wasobtained as in Example 4-3.

Example 4-10

The same procedure as in Example 4-3 was conducted, except that cesiumcarbonate was used in place of the calcium acetate monohydrate and thatthe maximum temperature of the heat medium in the first-stage reactionwas changed. The amount of the monomers distilled off was slightlylarger and the polymerization period was longer, as compared with thosein Example 4-3. The difference between the proportion of each dihydroxycompound fed as a starting material and the proportion of structuralunits of the dihydroxy compound in the polycarbonate resin obtained wasslightly larger than in Example 4-3.

Example 4-11

The same procedure as in Example 4-1 was conducted, except that calciumacetate monohydrate was introduced in an amount of 5.00×10⁻⁶ mol permole of all dihydroxy compounds and that the maximum temperature of theheat medium in the first-stage reaction was changed to 248° C. As inExample 4-1, the difference between the proportion of each dihydroxycompound fed as a starting material and the proportion of structuralunits of the dihydroxy compound in the polycarbonate resin obtained wassmall. However, slight coloration was observed.

Comparative Example 4-1

The same procedure as in Example 4-10 was conducted, except that in thefirst and second stages, the reflux condenser was bypassed and not used.In the second stage, the given power was not reached even when 180minutes had passed since the pressure had become 1 kPa. The polymerhence was discharged. The amount of the monomers distilled off waslarge, and the difference between the proportion of each dihydroxycompound fed as a starting material and the proportion of structuralunits of the dihydroxy compound in the polycarbonate resin obtained waslarge. In addition, the polycarbonate resin obtained had enhancedyellowness and impaired light resistance.

Comparative Example 4-2

The same procedure as in Comparative Example 4-1 was conducted, exceptthat the first stage was performed in the following manner. Thestarting-material mixture was evenly melted at 100° C., and the internaltemperature was thereafter elevated to 220° C. over 60 minutes. Pressurereduction was initiated at the time when the internal temperaturereached 220° C., and the system was regulated so that the pressurebecame 13.3 kPa over 120 minutes.

In the second stage, the given power was not reached even when 180minutes had passed since the pressure had become 1 kPa. The polymerhence was discharged. Although smaller than in Comparative Example 4-1,the amount of the monomers distilled off was still large. In addition,the difference between the proportion of each dihydroxy compound fed asa starting material and the proportion of structural units of thedihydroxy compound in the polycarbonate resin obtained was large.

Comparative Example 4-3

The same procedure as in Example 4-1 was conducted, except that thefirst-stage reaction was performed by a method including evenly meltingthe starting-material mixture at 100° C., thereafter elevating theinternal temperature to 250° C. over 40 minutes, initiating pressurereduction at the time when the internal temperature reached 250° C., andregulating the system so that the pressure became 13.3 kPa over 90minutes, and that the maximum temperature of the heat medium in thefirst-stage reaction was changed to 275° C. In the second stage, thegiven power was not reached even when 180 minutes had passed since thepressure had become 1 kPa. The polymer hence was discharged. The amountof the monomers distilled off was large, and the difference between theproportion of each dihydroxy compound fed as a starting material and theproportion of structural units of the dihydroxy compound in thepolycarbonate resin obtained was large. In addition, the polycarbonateresin obtained had too low a viscosity and was unable to be molded.

Reference Example First-Stage Reaction

Into a polymerization reactor having a capacity of 0.5 L which was madeof glass and equipped with a stirrer and a distillate tube connected toa vacuum pump were introduced 0.530 mol of ISB, 0.227 mol of CHDM, and0.773 mol of DPC which had been purified by distillation to reduce thechloride ion concentration thereof to 10 ppb or less. Calcium acetatemonohydrate in the form of an aqueous solution was introduced in anamount of 1.25×10⁻⁶ mol per mole of all dihydroxy compounds. Thereafter,nitrogen displacement was sufficiently conducted. Subsequently, thereactor was immersed in an oil bath, and stirring was initiated at thetime when the temperature of the liquid reaction mixture (often referredto as internal temperature) reached 100° C. The contents were melted andhomogenized while keeping the internal temperature at 100° C.Thereafter, heating was initiated to elevate the internal temperature to220° C. over 40 minutes. Pressure reduction was initiated at the timewhen the internal temperature reached 220° C., and the system wasregulated so that the pressure became 13.3 kPa over 90 minutes. Upon theinitiation of pressure reduction, the vapor of phenol which had beengenerated by the reaction rapidly began to be distilled off. Thetemperature of the oil bath was suitably regulated so that the internaltemperature was kept constant at 220° C. The temperature of the oil bathwas regulated to 224° C. during the period when phenol was distilled offin an increased amount, and was regulated so as to be lower than 224° C.during the other periods.

After the internal pressure was reduced to 13.3 kPa, the contents wereheld for further 60 minutes while maintaining that pressure. Thus, apolycarbonate oligomer was obtained.

The phenol which generated as a by-product of the polymerizationreaction and the monomers which were distilled off were introduced intoa condenser (inlet temperature of coolant, 45° C.) and recovered. Thephenol which was distilled off in this stage amounted to 90% of atheoretical distillation removal amount.

(Second-Stage Reaction)

Subsequently, the oil bath was heated and pressure reduction wasinitiated. The internal temperature was elevated to 220° C. and thepressure was reduced to 200 Pa, over 60 minutes. Thereafter, theinternal temperature was elevated to 230° C. and the pressure wasreduced to 133 Pa or below, over 20 minutes. At the time when a givenstirring power was reached, the pressure was returned to atmosphericpressure. The contents were discharged in the form of a strand. In thisoperation, the period from the time when the pressure became 1 kPa tothe time when the given stirring power was reached was measured. Thephenol which generated as a by-product of the polymerization reactionand the monomers which were distilled off were introduced into thecondenser (inlet temperature of coolant, 45° C.) and recovered, as inthe first-stage reaction. Furthermore, the fraction which had not beencondensed in the condenser was recovered with a cold trap disposeddownstream from the condenser.

The fractions recovered through the reflux condenser, condenser, andcold trap in each reaction stage were weighed and examined forcomposition to determine the amounts of the by-product phenol andmonomers which had been distilled off. The thus-determined weights ofthe monomers distilled off in the respective stages were summed up, andthe ratio of the total to the amount of the monomers fed as startingmaterials was calculated and shown in Table 4.

TABLE 4 Example 4-1 4-2 4-3 4-4 4-5 4-6 4-7 4-8 Starting Amount ofcatalyst Mg μmol per — — — — — 2.50 — — materials used (metal Ca mol of1.25 1.25 2.50 0.90 0.25 — — — amount) Ba dihydroxy — — — — — — 2.50 —Li compounds — — — — — — — 2.50 Cs — — — — — — — — Monomers used ISB mol% 70.0 50.0 70.0 70.0 70.0 70.0 70.0 70.0 CHDM 30.0 50.0 30.0 30.0 30.030.0 30.0 30.0 DEG — — — — — — — — DPC 100.0 100.0 100.0 100.0 100.0100.0 100.0 100.0 Production Maximum temperature of ° C. 242 240 244 239233 239 237 240 conditions heating medium in first stage Temperature ofliquid ° C. 220 220 220 220 220 220 220 220 reaction mixture (internaltemperature) in first stage Difference between maximum ° C. 22 20 24 1913 19 17 20 heat medium temperature and internal temperature in firststage Temperature of coolant introduced ° C. 100 100 100 100 100 100 100100 into reflux condenser Period from 1 kPa to min 60 45 30 80 170 13080 30 polymerization termination Poly- Molar proportion ISB (a) mol %70.0 50.7 70.0 70.0 71.0 70.0 70.0 69.9 carbonate in percentage of CHDM(b) 30.0 49.3 30.0 30.0 29.0 30.0 30.0 30.1 resin structural units DEG(c) — — — — — — — — derived from each dihydroxy compound Difference of|(a − A)/A| — 0.000 0.014 0.000 0.000 0.014 0.000 0.000 0.001 proportionof |(b − B)/B| 0.000 0.014 0.000 0.000 0.033 0.000 0.000 0.003structural units |(c − C)/C| — — — — — — — — of each dihydroxy compoundConcentration of Na, K, and wt ppm 0.6 0.8 0.6 0.6 0.6 0.6 0.6 0.6 Cs(total) Concentration of Li wt ppm <0.05 <0.05 <0.05 <0.05 <0.05 <0.05<0.05 0.13 (Amount of phenol distilled wt % 94 96 96 92 85 94 93 93 offin first stage)/ (theoretical distillation removal amount) (Total amountof monomers wt % 0.6 1.1 0.4 1.0 1.5 0.5 0.7 0.4 distilled off)/(sum ofstarting-material monomers) Reduced viscosity dL/g 0.49 0.60 0.51 0.500.48 0.49 0.50 0.49 Concentration of terminal phenyl μeq/g 85 61 61 60110 100 90 64 groups Molded Light transmittance at 350 nm % 76 65 71 7967 71 65 70 article Light transmittance at 320 nm % 56 42 50 59 45 50 4350 L* value — 96.8 96.4 96.6 97.0 96.4 96.5 96.3 96.4 YI — 3.5 4.6 4.23.0 4.0 4.5 5.5 5.0 YI value after metal halide lamp — 5.4 6.6 7.0 4.85.7 7.6 9.0 8.0 irradiation Difference in YI value — 1.9 2.0 2.8 1.8 1.73.1 3.5 3.0 between before and after metal halide lamp irradiationComparative Example Example Reference 4-9 4-10 4-11 4-1 4-2 4-3 ExampleStarting Amount of catalyst Mg μmol per — — — — — — — materials used(metal Ca mol of 2.50 — 5.00 — —  1.25 — amount) Ba dihydroxy — — — — —— — Li compounds — — — — — — — Cs — 2.50 —  2.50  2.50 — 2.50 Monomersused ISB mol % 70.0 70.0 70.0  70.0  70.0  70.0 70.0 CHDM — 30.0 30.0 30.0  30.0  30.0 30.0 DEG 30.0 — — — — — — DPC 100.0 100.0 100.0 104.0104.0 104.0 102.0 Production Maximum temperature of ° C. 250 238 248 235230 275 224 conditions heating medium in first stage Temperature ofliquid ° C. 220 220 220 220 220 250 220 reaction mixture (internaltemperature) in first stage Difference between maximum ° C. 30 18 28  15 10  25 4 heat medium temperature and internal temperature in firststage Temperature of coolant introduced ° C. 100 100 100 none none nonenone into reflux condenser Period from 1 kPa to min 30 80 25 180* 180*180* 80 polymerization termination Poly- Molar proportion ISB (a) mol %70.5 70.6 70.0  72.0  71.5  76.3 71.0 carbonate in percentage of CHDM(b) — 29.4 30.0  28.0  28.5  23.7 29.0 resin structural units DEG (c)29.5 — — — — — — derived from each dihydroxy compound Difference of |(a− A)/A| — 0.007 0.009 0.000  0.029  0.021  0.090 0.014 proportion of |(b− B)/B| — 0.020 0.000  0.067  0.050  0.210 0.033 structural units |(c −C)/C| 0.017 — — — — — — of each dihydroxy compound Concentration of Na,K, and wt ppm 0.3 2.5 0.6  2.5  0.6  0.6 0.8 Cs (total) Concentration ofLi wt ppm <0.05 <0.05 <0.05  <0.05  <0.05  <0.05 <0.05 (Amount of phenoldistilled wt % 95 89 98  86  87  98 90 off in first stage)/ (theoreticaldistillation removal amount) (Total amount of monomers wt % 0.8 1.6 0.4 17.0  10.5  13.3 1.7 distilled off)/(sum of starting-material monomers)Reduced viscosity dL/g 0.62 0.48 0.50  0.42  0.45  0.29 0.48Concentration of terminal phenyl μeq/g 90 108 50 181 169 — — groupsMolded Light transmittance at 350 nm % 70 47 48  48  55 — — articleLight transmittance at 320 nm % 50 19 22  16  25 — — L* value — 96.596.2 95.5  95.8  96.0 — — YI — 4.9 8.0 12.0  10.5  8.8 — — YI valueafter metal halide lamp — 7.5 11.7 17.0  15.0  13.0 — — irradiationDifference in YI value — 2.6 3.7 5.0  4.5  4.2 — — between before andafter metal halide lamp irradiation *Given power was not reached.

While the invention has been described in detail and with reference tospecific embodiments thereof, it will be apparent to one skilled in theart that various changes and modifications can be made therein withoutdeparting from the spirit and scope thereof. This application is basedon a Japanese patent application filed on Nov. 30, 2009 (Application No.2009-272413), a Japanese patent application filed on Nov. 30, 2009(Application No. 2009-272414), a Japanese patent application filed onNov. 30, 2009 (Application No. 2009-272415), and a Japanese patentapplication filed on Dec. 11, 2009 (Application No. 2009-281977), thecontents thereof being incorporated herein by reference.

INDUSTRIAL APPLICABILITY

The polycarbonate resins of the invention have excellent transparency,hue, heat resistance, thermal stability, and mechanical strength andfurther have excellent optical properties. Consequently, it is possibleto provide materials for use in a wide range of fields including thefield of injection molding, such as electrical/electronic parts andautomotive parts, the field of films and sheets, the field of bottlesand containers in which heat resistance is required, lens applicationssuch as camera lenses, finder lenses, and lenses for CCDs or CMOSs,films or sheets such as retardation films, diffusing sheets, andpolarizing films which are utilized in liquid-crystal or plasma displaysand the like, optical disks, optical materials, optical parts, andbinders for fixing colorants, charge transfer agents, etc.

Furthermore, according to the processes for polycarbonate resinproduction of the invention, it is possible to efficiently and stablyproduce a polycarbonate resin which has excellent light resistance,transparency, hue, heat resistance, thermal stability, and mechanicalstrength and which stably shows these performances.

1. A polycarbonate resin which at least contains structural unitsderived from a dihydroxy compound having the portion represented by thefollowing general formula (1) as part of the structure thereof, thepolycarbonate resin giving a molded object (thickness, 3 mm) which has alight transmittance, as measured at a wavelength of 350 nm, of 60% orhigher.[Chem. 1]CH₂—O  (1) (The case where the portion represented by general formula(1) is part of —CH₂—O—H is excluded.)
 2. The polycarbonate resin asclaimed in claim 1, wherein the molded object (thickness, 3 mm) formedfrom the polycarbonate resin has a light transmittance, as measured at awavelength of 320 nm, of 30% or higher.
 3. The polycarbonate resin asclaimed in claim 1, wherein the molded object (thickness, 3 mm) formedfrom the polycarbonate resin has a yellowness index (YI) value, asmeasured with respect to transmitted light in accordance with ASTMD1925-70, of 12 or less after having been irradiated with light for 100hours using a metal halide lamp in an environment of 63° C. and arelative humidity of 50% at an irradiance for the wavelength range of300-400 nm of 1.5 kW/m².
 4. The polycarbonate resin as claimed in claim1, wherein the molded object (thickness, 3 mm) formed from thepolycarbonate resin has an initial yellowness index value of 10 or less.5. The polycarbonate resin as claimed in claim 1, wherein the differencebetween the initial yellowness index value of the molded object(thickness, 3 mm) formed from the polycarbonate resin and the yellownessindex (YI) value thereof measured with respect to transmitted light inaccordance with ASTM D1925-70 after the molded object has beenirradiated with light for 100 hours using a metal halide lamp in anenvironment of 63° C. and a relative humidity of 50% at an irradiancefor the wavelength range of 300-400 nm of 1.5 kW/m² is 6 or less interms of absolute value.
 6. The polycarbonate resin as claimed in claim1, wherein the molded object (thickness, 3 mm) formed from thepolycarbonate resin has an L* value of 96.3 or higher.
 7. Thepolycarbonate resin as claimed in claim 1 which contains a carbonicdiester represented by the following general formula (2) in an amount of60 weight ppm or less.

(In general formula (2), A¹ and A² each independently are a substitutedor unsubstituted aliphatic group having 1-18 carbon atoms or asubstituted or unsubstituted aromatic group.)
 8. The polycarbonate resinas claimed in claim 1 which contains an aromatic monohydroxy compound inan amount of 700 weight ppm or less.
 9. The polycarbonate resin asclaimed in claim 1 which has a total content of sodium, potassium, andcesium of 1 weight ppm or less in terms of metal amount.
 10. Thepolycarbonate resin as claimed in claim 1, wherein the concentration ofthe end group represented by the following general formula (3) in thepolycarbonate resin is 20-160 μeq/g.


11. The polycarbonate resin as claimed in claim 1 which satisfiesA/(A+B)≦0.1, wherein A is the number of moles of the H bonded to thearomatic rings contained in the polycarbonate resin and B is the numberof moles of the H bonded to the part other than the aromatic rings. 12.The polycarbonate resin as claimed in claim 1, wherein the dihydroxycompound having the portion represented by general formula (1) as partof the structure thereof is a dihydroxy compound represented by thefollowing general formula (4).


13. The polycarbonate resin as claimed in claim 1 which further containsstructural units derived from at least one compound selected from thegroup consisting of aliphatic dihydroxy compounds and alicyclicdihydroxy compounds.
 14. The polycarbonate resin as claimed in claim 1which is obtained by condensation-polymerizing a dihydroxy compoundhaving the portion represented by general formula (1) as part of thestructure thereof with a carbonic diester represented by the followinggeneral formula (2) in the presence of a catalyst.

(In general formula (2), A¹ and A² each independently are a substitutedor unsubstituted aliphatic group having 1-18 carbon atoms or asubstituted or unsubstituted aromatic group.)
 15. The polycarbonateresin as claimed in claim 14, wherein the catalyst comprises one or morecompounds of at least one metal selected from the group consisting oflithium and the Group-2 metals of the long-form periodic table, and thetotal amount of these compounds is 20 μmol or less in terms of metalamount per mole of the dihydroxy compound used.
 16. The polycarbonateresin as claimed in claim 1 which has been obtained using as a catalystat least one metal compound selected from the group consisting ofmagnesium compounds and calcium compounds, the polycarbonate resinhaving a total content of lithium, sodium, potassium, and cesium of 1weight ppm or less in terms of metal amount.
 17. A polycarbonate resinwhich at least contains structural units derived from a dihydroxycompound having the portion represented by the following general formula(1) as part of the structure thereof, the polycarbonate resin giving amolded object (thickness, 3 mm) which has a yellowness index (YI) value,as measured with respect to transmitted light in accordance with ASTMD1925-70, of 12 or less after having been irradiated with light for 100hours using a metal halide lamp in an environment of 63° C. and arelative humidity of 50% at an irradiance for the wavelength range of300-400 nm of 1.5 kW/m².[Chem. 6]CH₂—O  (1) (The case where the portion represented by general formula(1) is part of —CH₂—O—H is excluded.)
 18. The polycarbonate resin asclaimed in claim 17, wherein the molded object (thickness, 3 mm) formedfrom the polycarbonate resin has an initial yellowness index value of 10or less.
 19. The polycarbonate resin as claimed in claim 17, wherein thedifference between the initial yellowness index value of the moldedobject (thickness, 3 mm) formed from the polycarbonate resin and theyellowness index (YI) value thereof measured with respect to transmittedlight in accordance with ASTM D1925-70 after the molded object has beenirradiated with light for 100 hours using a metal halide lamp in anenvironment of 63° C. and a relative humidity of 50% at an irradiancefor the wavelength range of 300-400 nm of 1.5 kW/m² is 6 or less interms of absolute value.
 20. The polycarbonate resin as claimed in claim17, wherein the molded object (thickness, 3 mm) formed from thepolycarbonate resin has a light transmittance, as measured at awavelength of 350 nm, of 60% or higher.
 21. A polycarbonate resinobtained by condensation-polymerizing at least one dihydroxy compoundincluding a dihydroxy compound which has the portion represented by thefollowing general formula (1) as part of the structure thereof with acarbonic diester represented by the following general formula (2) in thepresence of a catalyst, the catalyst comprising one or more compoundscontaining at least one metal selected from the group consisting oflithium and the Group-2 metals of the long-form periodic table, thepolycarbonate resin having a content of the metal-containing compoundsof 20 μmol or less in terms of metal amount per mole of the dihydroxycompound and containing an aromatic monohydroxy compound in an amount of700 weight ppm or less.[Chem. 7]CH₂—O  (1) (The case where the portion represented by general formula(1) is part of —CH₂—O—H is excluded.)

(In general formula (2), A¹ and A² each independently are a substitutedor unsubstituted aliphatic group having 1-18 carbon atoms or asubstituted or unsubstituted aromatic group.)
 22. The polycarbonateresin as claimed in claim 21, wherein the catalyst comprises at leastone metal compound selected from the group consisting of magnesiumcompounds and calcium compounds.
 23. The polycarbonate resin as claimedin claim 21 which has a total content of sodium, potassium, and cesiumof 1 weight ppm or less in terms of metal amount.
 24. The polycarbonateresin as claimed in claim 21 which has a total content of lithium,sodium, potassium, and cesium of 1 weight ppm or less in terms of metalamount.
 25. The polycarbonate resin as claimed in claim 21 whichcontains the carbonic diester represented by general formula (2) in anamount of 60 weight ppm or less.
 26. The polycarbonate resin as claimedin claim 21, wherein the dihydroxy compound having the portionrepresented by general formula (1) as part of the structure thereof is acompound represented by the following general formula (4).


27. The polycarbonate resin as claimed in claim 21 which containsstructural units derived from the dihydroxy compound that has theportion represented by general formula (1) as part of the structurethereof and further contains structural units derived from at least onecompound selected from the group consisting of aliphatic dihydroxycompounds and alicyclic dihydroxy compounds.
 28. The polycarbonate resinas claimed in claim 21, wherein the concentration of the end grouprepresented by the following general formula (3) in the polycarbonateresin is 20-160 μeq/g.


29. The polycarbonate resin as claimed in claim 21 which satisfiesA/(A+B)≦0.1, wherein A is the number of moles of the H bonded to thearomatic rings contained in the polycarbonate resin and B is the numberof moles of the H bonded to the part other than the aromatic rings. 30.The polycarbonate resin as claimed in claim 21, wherein a molded object(thickness, 3 mm) formed from the polycarbonate resin has a lighttransmittance, as measured at a wavelength of 350 nm, of 60% or higher.31. The polycarbonate resin as claimed in claim 21, wherein a moldedobject (thickness, 3 mm) formed from the polycarbonate resin has a lighttransmittance, as measured at a wavelength of 320 nm, of 30% or higher.32. The polycarbonate resin as claimed in claim 21, wherein a moldedobject (thickness, 3 mm) formed from the polycarbonate resin has ayellowness index (YI) value, as measured with respect to transmittedlight in accordance with ASTM D1925-70, of 12 or less after having beenirradiated with light for 100 hours using a metal halide lamp in anenvironment of 63° C. and a relative humidity of 50% at an irradiancefor the wavelength range of 300-400 nm of 1.5 kW/m².
 33. Thepolycarbonate resin as claimed in claim 21, wherein a molded object(thickness, 3 mm) formed from the polycarbonate resin has an initialyellowness index value of 10 or less.
 34. The polycarbonate resin asclaimed in claim 21, wherein the difference between the initialyellowness index value of a molded object (thickness, 3 mm) formed fromthe polycarbonate resin and the yellowness index (YI) value thereofmeasured with respect to transmitted light in accordance with ASTMD1925-70 after the molded object has been irradiated with light for 100hours using a metal halide lamp in an environment of 63° C. and arelative humidity of 50% at an irradiance for the wavelength range of300-400 nm of 1.5 kW/m² is 6 or less in terms of absolute value.
 35. Amolded polycarbonate resin obtained by molding the polycarbonate resinaccording to any one of claims 1 to
 34. 36. The molded polycarbonateresin as claimed in claim 35 which is a molded article obtained byinjection molding.
 37. A process for producing a polycarbonate resinusing a carbonic diester and at least one dihydroxy compound asstarting-material monomers and a catalyst, by condensation-polymerizingthe starting-material monomers by means of a transesterificationreaction using a plurality of reactors in multiple stages, wherein thedihydroxy compound comprises a dihydroxy compound having the portionrepresented by the following general formula (1) as part of thestructure thereof, at least one of the reactors from which themonohydroxy compound generated as a by-product of thetransesterification reaction is distilled off in an amount at least 20%of a theoretical distillation removal amount is a reactor which has acapacity of 20 L or more and which is equipped with a heating means forheating the reactor by means of a heating medium and further equippedwith a reflux condenser, the difference between the temperature of theheating medium and the temperature of the liquid reaction mixturepresent in the reactor being 5° C. or more, and the total amount of themonomers which are distilled off in all reaction stages is up to 10% byweight of the sum of the starting-material monomers.[Chem. 11]CH₂—O  (1) (The case where the portion represented by general formula(1) is part of —CH₂—O—H is excluded.)
 38. A process for producing apolycarbonate resin using a carbonic diester and at least one dihydroxycompound as starting-material monomers and a catalyst, bycondensation-polymerizing the starting-material monomers by means of atransesterification reaction using a plurality of reactors in multiplestages, wherein the dihydroxy compound comprises a plurality ofdihydroxy compounds, at least one of which is a dihydroxy compoundhaving the portion represented by the following general formula (1) aspart of the structure thereof, at least one of the reactors from whichthe monohydroxy compound generated as a by-product of thetransesterification reaction is distilled off in an amount at least 20%of a theoretical distillation removal amount is a reactor which has acapacity of 20 L or more and which is equipped with a heating means forheating the reactor by means of a heating medium and further equippedwith a reflux condenser, the difference between the temperature of theheating medium and the temperature of the liquid reaction mixturepresent in the reactor being 5° C. or more, and the value obtained bydividing the difference between the molar proportion in percentage ofeach dihydroxy compound which is being fed as a starting material to thereactors and the molar proportion in percentage of structural units ofthe dihydroxy compound which are contained in the resultantpolycarbonate resin by the molar proportion in percentage of thedihydroxy compound which is being fed is 0.03 or less in terms ofabsolute value with respect to at least one dihydroxy compound and isnot larger than 0.05 in terms of absolute value with respect to each ofall dihydroxy compounds.[Chem. 12]CH₂—O  (1) (The case where the portion represented by general formula(1) is part of —CH₂—O—H is excluded.)
 39. The process for producing apolycarbonate resin as claimed in claim 37 or 38, wherein the dihydroxycompound comprises at least one dihydroxy compound which has a boilingpoint at atmospheric pressure of 300° C. or lower.
 40. The process forproducing a polycarbonate resin as claimed in claim 37 or 38, wherein atleast three reactors are used.
 41. The process for producing apolycarbonate resin as claimed in claim 37 or 38, wherein a coolant isintroduced into the reflux condenser, the coolant having a temperatureof 45-180° C. as measured at the inlet of the reflex condenser.
 42. Theprocess for producing a polycarbonate resin as claimed in claim 37 or38, wherein the total amount of monomers which are distilled off in allreaction stages is 3% by weight or less based on the sum of thestarting-material monomers.
 43. The process for producing apolycarbonate resin as claimed in claim 37 or 38, wherein one or morecompounds of at least one metal selected from the group consisting oflithium and the Group-2 metals of the long-form periodic table aresupplied as the catalyst to the first reactor from which the monohydroxycompound generated as a by-product of the transesterification reactionis distilled off in an amount of at least 20% of a theoreticaldistillation removal amount, the metal compounds being used in an amountof 20 μmol or less in terms of the total amount of the metal atomsthereof per mole of all dihydroxy compounds used as starting materials.44. The process for producing a polycarbonate resin as claimed in claim43, wherein the catalyst comprises at least one metal compound selectedfrom the group consisting of magnesium compounds and calcium compounds.45. The process for producing a polycarbonate resin as claimed in claim37 or 38, wherein the liquid reaction mixture in all reaction stages hasa maximum temperature lower than 250° C.
 46. The process for producing apolycarbonate resin as claimed in claim 37 or 38, wherein the heatingmedium has a maximum temperature lower than 265° C.
 47. The process forproducing a polycarbonate resin as claimed in claim 37 or 38, whereinthe dihydroxy compound comprises a compound of the following generalformula (4) and at least one compound selected from the group consistingof aliphatic dihydroxy compounds and alicyclic dihydroxy compounds.


48. A polycarbonate resin obtained by the process according to any oneof claims 37 to 47, the polycarbonate resin giving a molded object(thickness, 3 mm) which has a light transmittance, as measured at awavelength of 350 nm, of 60% or higher.
 49. A polycarbonate resinobtained by the process according to any one of claims 37 to 47, thepolycarbonate resin giving a molded object (thickness, 3 mm) which has alight transmittance, as measured at a wavelength of 320 nm, of 30% orhigher.
 50. A polycarbonate resin obtained by the process according toany one of claims 37 to 47, the polycarbonate resin giving a moldedobject (thickness, 3 mm) which has a yellowness index (YI) value, asmeasured with respect to transmitted light in accordance with ASTMD1925-70, of 12 or less after having been irradiated with light for 100hours using a metal halide lamp in an environment of 63° C. and arelative humidity of 50% at an irradiance for the wavelength range of300-400 nm of 1.5 kW/m².
 51. A polycarbonate resin obtained by theprocess according to any one of claims 37 to 47, the polycarbonate resingiving a molded object (thickness, 3 mm) which has an initial yellownessindex value of 10 or less.
 52. A polycarbonate resin obtained by theprocess according to any one of claims 37 to 47, wherein the differencebetween the initial yellowness index value of a molded object(thickness, 3 mm) formed from the polycarbonate resin and the yellownessindex (YI) value thereof measured with respect to transmitted light inaccordance with ASTM D1925-70 after the molded object has beenirradiated with light for 100 hours using a metal halide lamp in anenvironment of 63° C. and a relative humidity of 50% at an irradiancefor the wavelength range of 300-400 nm of 1.5 kW/m² is 6 or less interms of absolute value.
 53. A polycarbonate resin obtained by theprocess according to any one of claims 37 to 47, the polycarbonate resingiving a molded object (thickness, 3 mm) which has an L* value of 96.3or higher.